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September,  1922 


No, 


DEMAND  for  the  educational 
papers  relating  to  principles 
and  practice  of  industrial  heating 
that  we  have  issued,  has  led  to 
their  revision  and  publication  in 
this  convenient  form,  to  better 
meet  requirements  for  a  supple- 
mentary textbook  for  shop  train- 
ing classes,  vocational  schools, 
colleges,  etc.,  as  well  as  for  the 
man  in  the  shop  and  others 
interested  in  the  subject. 


HE  purpose  of  this  booklet  is  to  draw  attention  to  essential  factors  governing  the  quality  and 
cost  of  products  subjected  to  the  action  of  heat  in  the  process  of  manufacture,  and  the  selection 
and  use  of  equipment,  fuel  or  electricity  necessary  to  produce  better  results  at  lower  cost. 

The  influence  of  heat  upon  the  quality  and  cost  of  practically  all  manufactured  products,  and  the 
comparatively  inefficient  methods  in  general  use,  indicate  the  necessity  of  developing  a  broader  view  of 
the  industrial  heating  problem. 

The  demand  for  better  and  cheaper  products  can  only  be  met  with  better  methods  of  heating  and 
handling,  better  equipment,  and  above  all,  men  better  qualified  to  understand  and  properly  apply  in  practice 
the  simple  principles  of  one  of  the  oldest  and  most  important,  though  indifferently  practiced,  industrial  arts. 

The  views  outlined  are  the  result  of  years  of  practical  experience  with  a  great  variety  of  heating  opera- 
tions and  direct  contact  with  actual  manufacturing  conditions.  This  has  taught  the  necessity  for  a  better 
understanding  of  the  underlying  principles  and  purposes  of  industrial  heating  operations,  the  results  of 
which  should  be  measured  in  terms  of  quality  and  cost  of  finished  product — not  merely  cost  of  fuel  or 
labor,  mere  tonnage  of  output,  nor  indication  of  temperature  control.  Such  factors  are  too  generally 
accepted  as  determinative,  although  they  bear  about  the  same  relation  to  the  result  sought  in  industrial 
heating  as  in  illumination  or  transportation. 


CONTENTS 


TITLE  PAGE 

Variety  of  Industrial  Heating  Processes         ...         3 

Factors  Governing  Quality  and  Cost  of  Heat-Treated 
Products  .  4 

Relation  of  Temperature  Control  to  Uniformly  Heated 
Product .6 

Factors  Affecting  Time  and  Method  of  Heating  and 
Cooling  ........  8 

Influence  of  Furnace  Design  on  Cost  of  Production  .       1 0 

Selection  of  Furnaces  .          ..         .          .          .          .12 

Illustrations  of  Practical  Methods  of  Heating  and 
Handling,  and  the  Variety  of  Furnace  Designs 
employed  in  the  Metallurgical,  Chemical,  Ceramic  and 
other  industries  .  14-25 


>      TITLE  PAGE 

Scope  and  Limitations  of  Regenerative  Furnaces      .  .       26 

Relation  of  Type  and  Arrangement  of  Equipment 

to  Cost  of  Production      .          .          .          .          .  .28 

Relation  of  Price  of  Fuel  to  Cost  of  Production         .  .       30 

Factors  Governing  Selection  of  Fuel  or  Electricity   .  .32 

Comparati ve  Prices  of  Fuel  on  B.  t.  u.  Basis    .          .  .34 

Comparative  Heating  Value  of  Industrial  Fuel  Gases  .       36 

Composition  of  Industrial  Fuel  Gases     .          .          .  .38 
Utilization  of  Fuel  Resources        .....       40 

Data  on  Heat    .  42 


Copyrighted  1922 
United  States  and  Great  Britain 


Variety  of  Industrial  Heating  Processes 


HE  variety  of  industrial  heating    processes    is 

rarely  realized  except  by  those  directly  concerned 
with  the  development  of  improved  methods  of 
heating  and  handling  to  meet  the  need  for  better 
and  cheaper  products  in  the  metallurgical,  chemical, 
ceramic  and  other  industries. 

The  use  of  heat  in  practically  every  branch  of  industry 

has  naturally  resulted  in  the  development  of  different  methods  of 
generating  heat  from  fuel  or  electricity;  many  different  methods 
for  the  application  and  utilization  of  heat  in  the  product,  and 
a  great  variety  in  furnace  design  and  equipment  for  handling  the 
material  to  be  heated  or  cooled. 

The  ever-increasing  demand  for  better  quality  and  lower 
cost  of  product  and  improvement  of  working  conditions  for 
the  operatives  directs  attention  to  the  ever-important  question  as 
to  the  manner  of  applying  heat  to  the  product,  which  is  so  directly 
related  to  quality,  and  the  influence  of  methods  of  heating  and 
handling  and  design  and  layout  of  furnace  equipment  upon  the 
cost  of  production. 

The  fundamental  principles  affecting  the  application  of 
heat  are  fixed,  but  there  is  an  untold  variety  in  method  of 
applying  these  principles  in  different  processes  to  meet  the  great 
variety  of  manufacturing  requirements  and  plant  conditions. 

In  certain  lines  of  manufacture,  experience  has  determined  the 
method  of  heat  application  and  the  physical  or  mechanical 
requirements  of  the  process,  which  in  a  large  measure  influence 
the  type,  size  and  general  arrangement  of  furnace  equipment  and 
the  form  of  fuel  or  electricity  to  employ  for  generating  heat. 

The  latitude  for  improvement  is  frequently  confined  to  re- 
finement in  design  of  furnace  and  auxiliary  equipment  and  in 
methods  of  generating  or  utilizing  heat  and  handling  material  to 
be  heated  and  cooled,  etc.  Often  there  is  apparently  little  room 
for  material  improvement  without  a  radical  change  in  the  nature 
of  the  manufacturing  process.  Frequently,  the  heat-treatment 
process  is  conducted  with  methods  and  equipment  which  are 
passable  under  certain  conditions  but  are  not  really  suited  to  the 
operation  in  hand,  making  it  exceedingly  difficult  to  materially 
improve  the  quality  or  decrease  the  cost  of  production.  Such 
conditions  generally  warrant  the  policy  of  ignoring  precedent, 
usually  the  result  of  circumstance,  and  starting  afresh  from  the 
fundamentals  of  the  problem. 

The  "human  element"  is  the  ultimate  controlling 
factor,  and  bears  about  the  same  relation  to  the  heat-treated 
products  of  the  shop  that  the  cook  bears  to  the  heat-treated 
products  of  the  kitchen.  The  common  and  wasteful  practice 
of  delegating  to  unskilled  men  the  control  of  important  heat- 
treatment  processes,  which  so  frequently  affect  subsequent 
operations  and  value  of  the  finished  product,  must  be  corrected 
in  the  practice  of  the  future. 

The  need  of  the  moment  is  for  improved  methods  of 
heating  and  handling  and  competent  operatives  or  super- 
visors who  understand  the  principles  affecting  the  generation, 
application  and  transfer  of  heat,  and  who  can  properly  employ 
furnaces,  fuel  or  electricity,  pyrometers,  etc.,  as  tools  for  the 
conduct  of  the  ever-important  work  of  "  heat  application.  " 

The  variety  of  methods  of  heating  and  handling,   and 

design  and  layout  of  furnaces  that  may  be  used  in  the  various 
industries,  is  generally  unknown  to  those  not  familiar  with  the 
wide  range  of  processes,  manufacturing  requirements  and  plant 
conditions,  and  the  possibility  of  effecting  improvement  in  one 
line  of  manufacture  through  experience  gained  by  practice  in 
others. 

To  the  average  man,  a  furnace  means  that  piece  of  necessary 
equipment  in  the  cellar  of  his  house  which  is  more  or  less  a 
nuisance  and  expense  for  six  to  nine  months  of  the  year. 


The  furnace  horizon  of  the  blacksmith  extends  very  little 
beyond  the  smith  fire  which  serves  for  general  forging  or  heat- 
treating  of  the  small  pieces  of  metal  to  which  it  is  adapted. 

The  drop  forger  sees  little  more  than  a  comparatively  small 
uncomfortable  furnace  with  an  uncovered  opening  in  front, 
through  which  the  material  to  be  heated  is  introduced  and  with- 
drawn. 

The  smith  accustomed  to  heavy  forge  work  and  steam  hammers 
or  hydraulic  presses  is  more  at  home  with  the  single-door  or 
multi-door  forge  furnace,  and  occasionally  with  some  type  of 
large  annealing  or  heat-treating  furnace. 

The  foundryman  engaged  in  the  production  of  iron  castings 
is  concerned  primarily  with  the  cupola  and  core  oven,  though  he 
may  be  familiar  with  air  furnaces  for  melting,  and  annealing 
ovens  if  malleable  iron  castings  also  are  produced. 

The  brass  founder  is  interested  in  little  beyond  his  crucible 
pit  fires  and  core  ovens,  though  in  some  instances  he  may  be  famil- 
iar with  the  tilting  type  of  crucible  or  reverberatory  melting 
furnaces,  or  with  electric  melting  furnaces. 

The  rolling  mill  man  producing  brass  or  copper  products  is 
familiar  with  coal  or  coke  pit  fires  for  melting  brass  in  crucibles, 
or  perhaps  with  the  tilting  type  of  electric  furnaces  in  which  the 
heat  may  be  released  through  induction,  or  through  some  form  of 
arc  or  resistance.  He  is  also  familiar  with  large  annealing  muffles; 
and,  if  engaged  in  the  manufacture  of  metal  specialties,  with  other 
types  of  furnaces  for  annealing,  brazing  and  other  operations.  If 
he  manufactures  brass  or  copper  wire  or  tubes,  he  will  undoubtedly 
know  various  types  and  sizes  of  billet  heating  furnaces,  and  even 
scaling  or  cake  heating  furnaces  if  producing  sheets  or  plates. 

Those  engaged  in  the  production  of  copper  are  primarily 
interested  in  smelting  furnaces  for  reducing  the  ore  or  in  large 
reverberatory  furnaces  for  refining  the  metal. 

Those  concerned  with  the  manufacture  of  steel  are  familiar 
with  furnaces  of  quite  different  designs,  there  being  a  wide  variety 
to  meet  the  requirements  for  steel  sheets,  wire,  rods,  pipes,  etc., 
starting  with  the  blast  furnace  and  followed  by  the  open  hearth, 
converter,  or  electric  melting  furnaces,  the  soaking  pit,  billet 
heater  and  other  units  to  meet  the  heating,  forging,  welding,  and 
annealing  requirements. 

Even  steel  mill  men  producing  structural  products  are 
frequently  unfamiliar  with  the  extremely  wide  variety  of  furnaces 
for  heating,  forging,  and  heat-treating  required  in  the  fabrication 
of  alloy  steels  into  manufactured  products,  ranging  from  heavy 
ordnance  to  the  smallest  needles. 

The  production  manager  in  the  large  automobile  or  similar 
plant  fabricating  large  quantities  of  different  kinds  of  metal  in 
assorted  sizes  has  a  broad  range  of  vision  in  the  industrial  heating 
field,  which  includes  many  of  the  furnaces  previously  referred  to 
and  various  types  of  other  furnaces  more  or  less  special  in  nature 
to  suit  production  requirements  for  normalizing,  hardening, 
carbonizing,  annealing,  and  miscellaneous  heat-treating  operations. 

The  chemical  engineer  is  confronted  with  some  interesting 
heating  problems,  which  require  a  wide  range  of  furnaces  adapted 
to  the  special  nature  of  his  processes  and  the  manufacturing 
requirements  and  plant  conditions  governing  his  practice. 

The  outline  of  principles  and  illustrations  of  their 
practical  application  in  different  lines  of  industry,  which 
follow,  have  been  compiled  in  the  belief  that  the  information  will 
be  of  benefit  to  those  interested  in  industrial  heating  processes, 
by  indicating  the  opportunities  for  improving  the  quality  and 
decreasing  the  cost  of  production  by  better  methods  of  heating 
and  handling,  which  frequently  result  from  proper  selection  and 
use  of  "FURNACE  AND  FUEL  TO  SUIT  CONDITIONS." 


Factors  Governing  Quality  and  Cost  of 
Heat-Treated  Products 


HE  importance  of  the  application  and  utiliza- 
tion of  heat  in  manufacturing  processes  should 
lead  to  a  thorough  consideration  of  the  factors 
that  govern  the  production  of  heat-treated  prod- 
ucts and  the  selection  and  use  of  furnaces  and 
fuels  as  a  means  to  that  end. 


Heat  in  one  way  or  another  affects  the  quality  and 
cost  of  practically  every  manufactured  product.  Its  in- 
fluence is  far-reaching,  particularly  in  the  manufacture  of  metal 
products,  yet  it  is  doubtful  if  there  is  another  manufacturing 
process  as  important  as  industrial  heating  so  generally  neglected 
and  misunderstood. 

The  selection  of  methods,  equipment  and  fuel  is  fre- 
quently made  difficult  by  widely  divergent  recommendations, 
based  on  opinion  or  prompted  by  commercial  interest,  which 
cloud  the  real  problem. 

Many  essential  factors  must  be  considered  in  the  problem 
as  a  whole,  including  intangible  values  which  cannot  be  definitely 
measured  on  account  of  evolution  in  the  art  and  the  ever-changing 
economic,  industrial  and  manufacturing  conditions. 

Essentials  may  be  overlooked  in  abstract  consideration 
of  related  details,  such  as  fuel  values,  methods  of  releasing  heat, 
temperature  control,  furnaces,  burners,  pyrometers,  control 
devices,  etc. 

V 

The  problem  boils  down  to  selecting  the  combination 

of  raw  materials,  methods,  production  equipment  and  facilities 
and  personnel,  which,  when  properly  adapted  to  individual 
manufacturing  requirements  and  plant  conditions,  will  most 
nearly  accomplish  the  result  sought,  i.  e.,  the  production  of 
quality  product  at  minimum  cost.  Every  detail,  technical  or 
otherwise,  is  but  a  means  to  this  end. 

It  is  as  much  a  waste  for  the  manufacturer  to  use  the  wrong 
form  of  heat  energy  (fuel  or  electricity),  regardless  of  its  cost  on 
the  basis  of  "  heat  unit  value, "  as  it  is  to  waste  the  right  form  of 
heat  energy  or  raw  material  in  furnaces  improperly  designed, 
constructed  or  operated,  regardless  of  heat  balance. 

Selection  may  be  simplified  by  consideration  of  the  factors 
outlined  by  the  chart  on  page  5,  which  govern  every  industrial 
heating  operation,  whether  it  be  baking  a  loaf  of  bread  or  melting, 
forging,  or  heat-treating  tons  of  steel. 

Quality  and  cost  of  finished  product  are  the  basic  factors. 

.There  are  many  contributing  factors,  including  the  human 
element,  any  one  of  which  may  influence  the  ultimate  result. 

Consideration  of  factors  affecting  quality  must  include 
the  manner  of  cooling  as  well  as  heating,  and  the  effect  of 
atmosphere.  Uniform  heating  prepares  material'  for  uniform 
heat-treatment;  the  adjustment  of  the  structure  and  final  set  in 
cooling  actually  determine  the  uniformity  of  the  heat-treatment. 

Uniformity  of  heating  and  cooling  is  governed  by  factors 
many  of  which  are  not  generally  considered.  Control  of 
furnace  chamber  temperature  is  but  one  of  the  factors  influencing 
uniformity  of  heated  product.  Of  primary  importance  are 
uniform  application  of  the  heating  or  cooling  medium  to  the 
surface  of  each  piece  of  the  charge,  the  rate  of  heating  or  cooling, 


degree  of  saturation  and  the  effect  of  atmosphere  inside  and  out- 
side the  furnace. 

Temperature  must  be  considered  with  the  element  of 
time  and  the  surface  exposure  of  each  piece  to  the  heating 
and  cooling  mediums.  The  relation  of  surface  to  mass  is 
the  basic  factor  determining  time  of  exposure,  other  conditions 
such  as  conductivity  of  material,  rate  of  heating  or  cooling,  etc., 
being  equal.  The  shape  of  the  individual  pieces,  affecting  the 
relation  of  surface  and  mass,  or  a  mere  change  in  shape  without  a 
change  in  weight  or  composition,  may  dictate  changes  in  the 
method  or  rate  of  heating,  cooling  or  handling.  With  highly 
figured  dies  or  irregularly  shaped  forgings  or  castings,  it  is 
desirable  to  heat  slowly  to  prevent  overheating  the  thin  sections 
or  sharp  corners,  which,  by  reason  of  large  surface  in  propor- 
tion to  mass,  are  heated  and  cooled  more  rapidly. 

The  all-important  work  of  properly  applying  heat  to 
the  product  is  frequently  neglected  by  consideration  of 
related  conditions,  such  as  "temperature  control,"  "fuel  values," 
methods  of  releasing  heat  through  combustion  or  electricity, 
or  methods  of  indicating  or  controlling  temperature. 

The  cost  of  heat  energy  in  the  form  of  fuel  or  electricity  is 
frequently  accepted  as  a  standard  by  which  to  measure  heating 
cost,  but  it  is  of  little  value  without  consideration  of  other 
factors  determining  quality  and  ultimate  cost  of  product. 

Fuel  cost,  which  includes  quantity  consumed  as  well  as  price, 
is  but  one  item  in  the  final  cost  of  heating,  just  as  it  is  but  one 

item  in  the  final  cost  of  illumination  or  transportation.  In  all 
cases,  the  design,  operation  and  suitability  of  the  appliance, 
whether  it  be  a  lamp,  boiler,  engine,  motor  truck  or  furnace,  must 
be  considered  in  relation  to  the  quality  and  cost  of  the  ultimate 
result.  Fuel  consumption  records  bear  about  the  same  relation  to 
manufacturing  or  transportation  costs  that  pyrometer  records 
bear  to  quality  of  product. 

Industrial  heating  results  cannot  be  measured,  as  in  power, 
illumination  or  transportation,  by  definite  standards,  such  as  the 
horse  power  hour,  kilowatt  hour,  candle  power  hour,  ton  mile,  etc., 
because  of  the  many  variable  factors  influencing  the  quality  and 
cost  of  finished  product. 

Cost  per  unit  of  given  quality— not  cost  of  fuel,  of  labor, 
of  tonnage  output,  nor  indication  of  temperature  control 
— is  the  determinative  test  of  an  industrial  heating  opera- 
tion. 

The  human  element  cannot  be  eliminated  by  devices 
which  govern  supply  of  heat  energy,  except  in  rare  cases  where 
the  manufacturing  routine  does  not  vary  in  essential  detail. 
Variations  in  size,  shape,  weight,  quantity,  rate  of  flow,  time  of 
exposure,  composition  of  material,  or  in  the  heating  or  cooling 
process,  require  skill  and  judgment  on  the  part  of  the  operative. 
Recognition  of  the  difference  between  control  of  temperature  and 
means  of  releasing  heat  on  the  one  hand,  and  control  of  other 
essential  factors  related  to  finished  product  on  the  other  hand, 
should  cause  appreciation  of  the  importance  of  the  human 
element. 

Low  first  cost  of  material,  or  fuel,  or  equipment,  or  labor  does 
not  assure  low  cost  of  quality  product.  Improvement  in 
quality  and  decrease  in  cost,  or  both,  will  result  only  from  a 
proper  co-ordination  of  all  factors. 


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Relation  of  Temperature  Control  to 
Uniformly  Heated  Product 


NDICATION  of  "temperature  control  is  fre- 
quently accepted  as  evidence  of  a  thermal  condi- 
tion suited  to  the  production  of  a  uniformly  heated 
product,  regardless  of  the  fact  that  indication  of 
uniform  furnace  temperature  does  not  of  itself 
establish  the  uniformity  of  a  heating  or  cooling 
process. 

Uniform  temperature  is  necessary  to  produce  uniformly  heated 
product,  but  heating  a  chamber  uniformly  and  uniformly 
heating  a  charge  within  that  chamber  are  two  distinct 
matters. 

Indication  of  temperature  control  is  misleading  without 
consideration  of  other  factors  affecting  the  uniform  heating  or 
cooling  of  the  product,  as  outlined  by  the  chart  on  page  7. 

Of  primary  importance  are  the  uniformity  of  heat  ap- 
plication to  the  surface  of  the  individual  piece,  the  time 
of  exposure  and  the  rate  of  heating.  Variation  in  product 
may  be  caused  by  differences  in  furnace  design,  in  placing  of 
charge  in  the  chamber,  in  the  time  of  exposure  and  in  rate  of 
heating  or  rate  of  charging  and  discharging,  resulting  in  differ- 
ence in  the  application  of  heat  to  the  charge,  without  any 
indication  of  chamber  temperature  variation. 

The  ideal  condition  for  the  production  of  properly  heated 
product  is  nearest  attained  when  the  heating  and  cooling  mediums 
are  uniformly  applied  to  the  entire  surface  of  each  piece  or  section 
in  the  same  manner,  at  the  same  temperature,  at  the  same  rate, 
for  the  same  time,  in  the  same  atmosphere,  in  equipment  properly 
adapted  to  the  nature  of  the  process,  production  requirements 
and  plant  conditions. 

The  relation  of  indicated  chamber  temperature  to  heated 
product  is  illustrated  by  the  diagram  on  page  7. 

The  pyrometer  chart  is  the  record  of  a  furnace  in  actual 
operation.  Although  it  might  be  assumed  that  a  charge  would  be 
uniformly  heated  in  any  furnace  recording  such  a  chart,  there  is 
a  marked  variation  in  the  heating  of  the  charge  in  many  of  the 
furnaces  (1  to  11)  even  though  the  indicated  chamber 
temperature  and  time  of  heating  are  the  same.  The  approx- 
imate locations  of  the  incompletely  heated  zones  are  shown  by  the 
shaded  sections. 

The  electric  furnaces  (5,  6,  7)  are  not  exceptions  to  the 
rule,  for  while  they  are  alike  in  manner  of  generating  and 
controlling  the  heat,  they  differ  in  manner  of  applying  it  and 
in  method  of  handling  the  charge. 

The  product  will  likewise  vary  in  uniformity  in  each  of 
these  furnaces,  depending  on  distribution  of  the  charge — 

mass  and  surface  exposed  to  heat — although  there  may  be  no 
variation  of  indicated  chamber  temperature  or  time  of  heating. 
Diagrams  "A"  to  "O"  illustrate  the  variation  from  uniformity 
resulting  from  different  methods  of  distributing  the  same  charge. 

The  rate  of  heat  input  must  be  intelligently  considered 
whenever  there  is  a  material  variation  in  the  mass  or  surface  of 
the  pieces.  Such  variations  may  warrant  changes  in  type  or 
design  of  furnace  in  order  to  control  the  rate  of  heating,  time  of 
exposure,  and  placing  of  the  charge  in  the  chamber,  independently 
of  the  manner  in  which  the  heat  itself  may  be  generated,  controlled 
or  indicated. 

With  the  method  of  loading  illustrated  by  diagram  12,  it  is 
apparent  that  if  the  pieces  of  the  charge  were  handled  individually, 
the  one  first  placed  in  the  chamber  would  be  the  last  withdrawn, 
and  the  piece  last  charged  the  first  withdrawn.  If  all  the  pieces 
of  the  charge  were  withdrawn  when  the  one  first  introduced  was 
fully  heated,  and  if  this  one  had  been  introduced  at  approximate 
working  chamber  temperature,  there  would  be  a  difference 
in  time  of  exposure  and  degree  of  saturation  of  all  the 
pieces.  If  the  pieces  were  placed  close  to  or  on  top  of  one  another, 


the  condition  would  be  still  more  unfavorable.  In  such  a  furnace, 
regardless  of  the  uniformity  of  temperature  or  method  of  generating 
or  applying  heat,  a  charge  will  not  be  heated  uniformly  unless  it  is 
introduced  and  withdrawn  as  a  unit,  or  unless  the  furnace  and 
charge  are  slowly  heated  together. 

A  cold  charge  placed  in  a  hot  furnace  will  absorb  heat 
rapidly,  causing  a  drop  in  chamber  temperature,  whether  it  be 
indicated  by  the  pyrometer  or  not.  The  temperature  drop  and 
time  of  recovery  will  be  greater  in  a  light  furnace  than  in  a  heavy 
furnace  of  the  same  type  and  chamber  area.  The  greater  heat 
storage  in  the  heavier  furnace  is  of  advantage  in  minimizing  such 
drop  and  time  of  recovery,  in  addition  to  effecting  economy 
in  operation. 

The  temperature  will  also  vary  with  the  regularity  of 
input  and  outgo  of  material  and  heat;  and  with  the  relation 
between  the  temperature,  mass  and  surface  exposure  of  material 
in  the  chamber,  and  the  temperature,  mass  and  surface  exposure 
of  material  which  follows.  The  actual  temperature  fluctuation 
will  decrease  with  the  subdivision  of  the  charge  as  the  torque  of  a 
gasoline  engine  or  diagram  of  pump  flow  becomes  more  uniform 
with  an  increase  in  the  number  of  cylinders. 

Determination  of  such  factors  as  placing  of  charge  in  the 
chamber,  methods  of  handling,  and  suitable  arrangement  of 
furnace  equipment,  etc.,  must  include  consideration  of  the 
manner  of  applying  heat  to  the  charge,  i.  e.,  whether  it  be 
transferred  by  radiation,  convection  or  forced  circulation  of 
chamber  atmosphere. 

While  in  both  fuel-fired  and  electrically  heated  furnaces  a  great 
deal  of  the  heat  is  transferred  by  radiation,  a  considerable  amount 
is  transferred  by  the  circulation  of  the  chamber  atmosphere. 

Heating  by  radiation  alone  is  frequently  undesirable  in 
fuel-fired  furnaces  of  the  muffle  type  or  in  electric  furnaces  in 
which  there  is  no  forced  circulation  of  the  heating  chamber 
atmosphere,  because  of  the  difficulty  of  properly  transferring 
heat  to  the  entire  surface  of  the  charge  or  individual  unit, 
and  the  consequent  possible  lack  of  uniformity. 

Much  of  the  heating  that  is  supposed  to  be  conducted 
solely  by  radiation  is  actually  performed  by  convection 
currents  brought  about  by  a  temperature  differential,  which 
naturally  creates  motion  and  prohibits  existence  of  the  so-called 
"quiescent  atmosphere."  The  rate  of  circulation  of  such 
convection  currents  is  influenced  by  the  temperature  differential 
and  the  relative  mass  and  exposed  surfaces  of  the  receiving  and 
emissive  bodies. 

Frequently,  as  in  the  operation  of  electrically  heated  japanning 
ovens  or  fuel-fired  furnaces  of  the  muffle  type,  in  the  chamber  of 
which  there  is  but  a  slight  temperature  differential,  it  is  necessary 
to  provide  for  forced  circulation  of  the  chamber  atmosphere  in 
order  to  permit  of  efficient  heat  transfer,  which  would  be  unnec- 
essary if  the  temperature  differential  were  greater. 

The  continuous  furnace  (13)  may  be  employed  in  a  variety 
of  designs  and  methods  of  heat  generation,  with  improved  quality 
of  product  resulting  from  uniformity  of  heat  application,  and 
time  and  rate  of  exposure,  and  with  lowered  operating  cost, 
resulting  from  the  efficient  method  of  handling  the  product  and 
directly  utilizing  the  heat.  The  field  of  usefulness  of  the  con- 
tinuous furnace,  however,  is  determined  by  the  size  and  shape  of 
the  pieces  to  be  heated,  as  well  as  by  the  quantity  and  regularity 
of  their  flow. 


Uniform    heating    is    a    relative    term, 
formity  is  rarely,  if  ever,  attained. 


Absolute      uni- 


Practical  uniformity  of  heated  product  is  secured  only  by  the 
proper  co-ordination  and  application  of  all  factors  essential  to 
the  selection  and  operation  of  industrial  heating  equipment. 


RELATION   OF  TEMPERATURE 


TO   HEATED    PRODUCT 


Factors  Affecting  Time  and  Method  of  Heating 

and  Cooling 


I  ME  —  the  period  required  for 
heating  or  cooling — is  a  vital 
factor  in  all  processes  involving 
the  application  of  heat. 


The  influence  of  the  "time 
factor"  is  not  generally  appre- 
ciated in  practice,  due  no  doubt  to  a  misunder- 
standing of  its  importance  and  the  many 
variables  that  affect  it.  Unwarranted  em- 
phasis on  "temperature  control"  as  the  es- 
sential element  in  heating  or  cooling  operations, 
and  "output,"  "fuel  consumption,"  etc.,  as  the 
determination  of  cost,  frequently  leads  to 
neglect  of  the  influence  of  the  time  and 
manner  of  exposure  and  the  rate  of  heating 
or  cooling  upon  quality  and  cost  of  the 
finished  product. 


HEATED - 


~TFMPEI»ATURE-rREQUIRED  IN   PROCESS 

*•  ^-  I 


UNIFORMITY  DESIRED 


CONDUCTIVITY  OF  MATERIAL 
-RATE  OF 


-TIHE- 


Control  of  time  and  rate  of  heating  or 
cooling  is  just  as  essential  as  control  of  temperature. 
Time  and  temperature  are  so  inseparably  linked  that  it  would  be 
well  to  associate  the  two  as  one  controlling  factor — "time- 
temperature."  The  use  of  such  a  term  may  tend  to  discourage 
the  usual  abstract  consideration  of  temperature  without  regard 
to  the  time  necessary  to  attain  a  given  temperature;  and  to 
encourage  the  thought  that  there  are  a  number  of  factors  in 
addition  to  control  of  temperature  that  influence  the  uniformity 
with  which  a  given  piece  is  heated  or  cooled. 

The  "time  factor"  is  just  as  important  in  heating  or 
cooling  operations  in  the  shop  as  it  is  in  the  cooking 
processes  in  the  kitchen,  where  its  influence  is  more  generally 
appreciated.  The  care  with  which  a  cook  exposes  a  dish  to  the 
heat  ("heat  application"),  the  attention  given  to  time  and  rate 
of  heating,  as  in  boiling  an  egg  or  baking  a  pie,  and  the  good 
results  that  generally  follow  the  operation  without  provision  for 
automatic  control  of  temperature,  suggest  application  of  the 
same  simple  principles  in  industrial  heating  operations.  Such  pro- 
cedure would  do  much  to  eliminate  the  irregularities  so  fre- 
quently disclosed  by  physical  tests,  regardless  of  evidence  in  the 
form  of  pyrometer  records  and  analyses  of  material  to  show  that 
such  irregularities  should  not  exist. 

The  viewpoint  of  the  engineer  with  reference  to  "the 
rate  at  which  heat  CAN  be  transferred"  to  save  time  or 
fuel  or  increase  production,  should  be  considered  with  the 
views  of  the  metallurgist  or  chemist  in  determining 
"the  rate  at  which  heat  SHOULD  be  transferred"  in  order 
to  effect  the  desired  results  in  quality  of  finished  product. 
The  result  of  the  heat-treating  operation  should  be  expressed  in 
terms  of  quality  and  cost  of  finished  product — not  cost  of  fuel 
or  labor,  mere  tonnage,  nor  indication  of  uniform  chamber 
temperature. 

The  ideal  condition  for  the  production  of  uniformly 
heated  product  is  nearest  attained  when  the  heating  or  cooling 
medium  is  uniformly  applied  to  the  entire  surface  of  each  section 
or  piece  and  to  each  piece  individually  in  the  same  manner,  at 
the  same  temperature,  at  the  same  rate,  for  the  same  time, 
in  the  same  atmosphere,  in  equipment  properly  adapted  to  the 
nature  of  the  process,  form  of  fuel  or  electricity  employed, 
manufacturing  requirements  and  plant  conditions. 

Temperature  is  a  more  or  less  fixed  factor,  determined  by 
the  nature  of  the  process  and  the  physical  or  chemical  require- 
ments of  the  product  to  be  heated  or  cooled.  It  should  be  con- 
sidered with  reference  to  the  distinction  between  temperature 
of  the  chamber  or  bath  in  which  a  piece  is  exposed  and  the 
temperature  throughout  the  piece  itself,  which  is  naturally 
affected  by  the  time  of  exposure  and  the  rate  of  heat  absorption. 


^-MEDIUM 

rHEATING 
^COOLING 


-DEGREE  OF  SATURATION  DESIRED 

I RATE  OF L_rHEATING-i  i-GASEOUS 

rl-CIRCULATION-f'-COOLING-^MEt"U*T-LIOUID 


rAPPLICATIONT 

H             OF  T 

I HP  AT 1 


rTHERMAL  UNIFORMITY  OF  HEATING  ZONE 
DESIGN  OF  HEATING  CHAMBER 


MATERIAL  IN  HEATING 
COMBUSTION  CHAMBER 
INLET  AND  OUTLET  PORTS 
HEATING  ELEMENTS 


"-POSITION  OF 


Fig.  3.      Factors  Determining  Uniformity  of  Heating  and  Cooling 


Time  of  heating  is  a  variable  factor  and  is  influenced  by  the 
manner  of  transferring  heat  to  or  from  the  surface  of  the  piece; 
the  manner  of  loading,  or  exposure;  the  relation  of  one  piece  to 
another  and  to  the  source  of  the  heat;  the  difference  between 
temperature  of  the  piece  and  the  chamber  or  bath  in  which  it  is 
exposed;  the  rate  of  circulation  over  the  surface;  conductivity 
of  the  material  of  which  the  piece  is  composed;  relation  of  the 
mass  of  the  charge  to  the  chamber  or  bath  in  which  it  is  exposed, 
and  other  factors  outlined  by  Fig.  3. 

Rate  of  heating  or  cooling  of  material  must  be  determined 
with  reference  to  the  physical  or  chemical  requirements  of  the 
finished  product,  and  with  reference  to  the  mass,  shape,  section, 
exposed  surface,  and  manner  of  exposure  of  the  material,  all  of 
which  affect  the  rate  at  which  it  SHOULD  be  heated  or  cooled, 
regardless  of  how  fast  heat  COULD  be  transferred. 

Rate  of  heat  transfer  affects  the  time  required  for  heating 
or  cooling,  and  exerts  material  influence  upon  quality 
of  the  finished  product.  It  should  be  considered  with  reference 
to  the  relation  of  the  condition  inside  of  the  piece  to  the  sections 
near  the  surface.  The  influence  of  variable  section,  shape 
or  surface  exposed  upon  the  rate  of  heating  or  cooling 
may  necessitate  slow  heating  or  preheating  in  order  that  the 
mass  may  be  well  saturated  before  being  subjected  to  the  final 
temperature.  Disregard  of  this  point  is  responsible  for  the  dif- 
ficulties that  frequently  follow  the  practice  of  maintaining  furnace 
temperatures  materially  higher  than  that  required  in  the  stock. 

The  relation  of  the  temperature  of  a  furnace  to  the 
temperature  at  the  outside  of  a  piece  is  not  necessarily  an 
indication  of  uniform  structure  unless  the  time  period  has  been 
sufficient  for  thorough  saturation  and  the  stock  properly  exposed 
to  the  heat.  A  difference  in  time  of  exposure  or  manner  of 
exposing  two  similar  pieces  at  the  same  temperature  may  result 
in  a  difference  in  structure. 

The  method  of  loading  a  furnace  affects  the  time  re- 
quired for  heating  the  individual  piece;  the  uniformity  of 
structure  of  each  piece  throughout  its  mass;  and  the  relation  of 
the  uniformity  of  each  piece  to  another.  The  influence  upon 
the  time  and  rate  of  heating  of  the  exposure  resulting  from  a  given 
manner  of  loading  and  variations  in  the  surface,  shape  and 
section,  may  be  illustrated  by  the  diagrams  in  Fig.  4. 

A  round  billet  of  given  mass  and  weight  placed  on  the 
hearth  of  a  furnace  (A)  will  heat  less  uniformly  and  at  a  different 
rate  than  if  placed  above  the  floor  (B)  to  permit  circulation  under- 
neath and  uniform  application  of  heat  to  the  entire  surface. 


. 


A  billet  of  the  same  mass  and  weight 
in  rectangular  form  will  heat  at  a 
different  rate  and  to  a  different  degree 
of  uniformity  if  placed  in  either  position 
on  account  of  the  relatively  larger  surface 
in  proportion  to  the  mass  at  the  corners, 
which  are  the  first  to  heat  up  and  the 
first  to  cool  off.  Even  though  the  shape 
of  the  rectangular  billet  may  permit  a 
higher  rate  of  absorption,  it  is  obvious 
that  the  difference  in  shape  may  ac- 
tually suggest  a  lower  rate  of  heat 
transfer  to  permit  a  slow  rate  of  heating, 
in  order  to  prevent  a  material  difference  in 
temperature  or  time  of  exposure  to  that 
temperature  between  the  corners  and 
center  of  the  mass. 

The  same  billet  in  the  form  of  an 
irregularly  shaped  crankshaft  or  axle 
with  variable  sections  will  heat  in  a 
still  different  manner  if  placed  in 
either  position  on  account  of  the  difference 
in  surface  and  section. 

A  gear  blank  (D)  will  absorb  heat  at  an 
entirely  different  rate  than  the  finished 
gear  (E),  on  account  of  the  difference  in 
section  incident  to  the  shape  of  the  teeth 
and  opening  for  the  shaft  keyway,  etc. 

A  similar  condition  may  result  from  the 
relation  of  the  pieces  to  each  other, 

even  in  a  chamber  that  shows  every  indi- 
cation of  uniform  temperature.  Thus, 
two  rectangular  pieces  placed  above  the 
floor,  with  provision  for  heat  application 
to  all  surfaces,  will  heat  at  a  different  rate 
and  to  a  different  degree  of  uniformity 
when  placed  in  contact  with  each  other(C). 


Fig.  4.     Illustrations 


Heating  in  baths  of  molten  metal, 
salts,  etc.,  is  generally  considered  to  be  an 
ideal  method  for  operations  in  which 

uniformity  of  heating  and  temperature  control  are  essential 
factors.  However,  the  difference  between  heating  in  a  molten 
bath  and  in  a  "bath"  of  gases  in  the  chamber  of  a  furnace  is 
not  as  great  as  is  generally  supposed.  The  essential  dif- 
ference is  in  the  influence  of  the  bath  upon  the  surface  of  the 
piece;  the  manner  of  exposure  and  the  resistance  of  the 
bath  to  rapid  transfer  of  heat. 

The  necessity  for  suspending  the  piece  in  a  bath  naturally 
results  in  an  ideal  condition  for  proper  "heat  application" 
to  the  surface,  and  eliminates  many  chances  for  error  likely 
to  result  from  improper  methods  of  loading  in  the  chamber  of 
a  furnace,  particularly  if  it  is  desired  to  localize  the  heat, 
as  in  hardening  the  cutting  section  of  a  tool. 

Inequalities  of  temperature  may  exist  throughout  a 
bath  without  indication  by  the  pyrometer  in  its  customary 
fixed  position,  as  may  be  observed  in  heating  the  bath  from  a 
cold  condition;  in  introducing  a  comparatively  large  mass  of 
cold  material ;  or  when  the  input  of  cold  material  does  not  cor- 
respond with  the  withdrawal  of  heated  material. 

The  use  of  a  bath  does  not  eliminate  the  necessity  for 
considering  the  time  element  with  reference  to  the  factors 
that  influence  the  rate  of  heat  transfer  and  uniformity  of  heating 
or  -cooling.  A  difference  in  relation  of  mass  and  surface,  due  to  a 
difference  in  shape  or  section,  naturally  affects  the  rate  of  heat 
transfer  and  the  time  required  for  saturation.  Thus,  if  a  tap 
were  suspended  in  a  bath  of  molten  metal  (F),the  comparatively 
thin  sections  would  reach  the  temperature  of  the  bath  before  the 
center  of  the  piece;  and  even  though  the  center  ultimately  attains 
the  same  temperature  (G)  ,the  fact  remains  that  the  thin  sections 
have  been  subjected  to  that  temperature  for  a  longer  time,  which 
of  itself  is  frequently  sufficient  to  create  a  difference  in  structure. 

This  illustrates  the  difference  between  uniform  tempera- 
ture in  a  furnace  and  uniformly  heated  product,  and  the 


of  influence  of  mass,  surface,  shape,  and  manner  of  exposure  upon  time 
and  uniformity  of  heating. 

necessity  for  considering  the  influence  of  the  factors  that  affect 
time  or  rate  of  heating,  as  well  as  the  factors  that  affect  control  of 
temperature.  Uniform  heating  is  a  relative  term.  Absolute 
uniformity  is  rarely,  if  ever,  attained. 

The  necessity  for  uniform  time  and  method  of  exposure 
and  rate  of  heating  or  cooling  to  produce  uniform  product 
indicates  the  need  for  a  method  of  heating,  cooling  and  handling 
that  will  provide  the  same  treatment  for  each  piece. 

"Batch  heating"  or  cooling  rarely  results  in  uniform 
product,  regardless  of  the  indication  of  uniform  chamber 
temperature,  because  of  the  lack  of  uniformity  in  method  and 
time  of  exposure  and  rate  of  heating  or  cooling.  Variation  is 
generally  disclosed  by  the  structural  difference  between  the  pieces 
at  the  outside  of  the  charge  and  those  at  the  center  or  bottom. 

The  advantages  of  the  continuous  furnace  (L)  in  providing 
a  regular  input  and  output  of  material,  and  control  of  the  factors 
affecting  time  and  rate  of  heating,  suggest  application  of  the 
principle  of  individual  treatment  whenever  the  manufacturing 
requirements  and  plant  conditions  will  so  permit. 

The  difference  between  control  of  temperature  in  a 
furnace  and  control  of  the  application  of  heat  to  the 
product  is  not  merely  a  function  of  controlling  the  input  of  heat- 
ing energy,  whether  it  be  fuel  or  electricity.  The  manner  in  which 
the  heat  is  applied  to  the  surface  of  the  piece,  which  very  largely 
reflects  the  design  and  method  of  operating  the  furnace,  is  of 
paramount  importance;  and  necessarily  involves  factors  affecting 
the  element  of  time  and  rate  of  heating  and  cooling,  which  are 
equally  as  important  as  factors  that  influence  control  of  tempera- 
ture. All  of  these  must  be  considered  in  order  to  produce  a 
product  as  uniform  as  the  pyrometer  indicates  it  should  be. 


Influence  of  Furnace  Design  on  Cost  of  Production 


HE   ultimate   cost   of   a   finished   product   of 

given  quality  is  governed  by  the  rate  of  production 
and  the  cost  of  operation. 

Because  of  the  many  variable  factors  governing 
the  quality  and  cost  of  product  (page  5),  the  selec- 
tion of  furnace  equipment  (page  13),  and  the 
selection  of  fuel  (page  33),  consistent  efforts  to  reduce  cost  of 
production  require  a  thorough  study  of  methods  of  heating  and 
handling  adapted  to  specific  manufacturing  requirements  and 
plant  conditions. 

The  influence  of  furnace  design  on  the  quality  and  cost 
of  product  is  illustrated  by  the  diagrams  on  page  11,  which  are 
examples  from  actual  practice. 

These  diagrams  illustrate  the  economy  attainable  by  the 
proper  use  of  furnaces  of  suitable  design,  the  selection  of  which  is 
based  upon  consideration  of  the  manufacturing  problem  as  a 
whole.  They  also  illustrate  the  economic  weakness  of  the  far  too 
common  practice  of  basing  selection  only  on  price  or  form  of  fuel, 
equipment  or  labor;  quantity  of  output;  temperature  control,  etc., 
without  reference  to  other  equally  essential  factors  affecting 
quality  and  cost  of  the  finished  product. 

There  are  no  fixed  standards  to  determine  definitely  the 
proper  form  of  equipment  or  fuel  to  use.  Each  must  be 
selected  with  reference  to  the  other,  and  the  suitability  of  the 
combination  to  the  heating  process,  manufacturing  requirements 
and  plant  conditions. 

Frequently  it  is  possible  to  better  the  quality  of  product 
by  adapting  an  improved  method  of  heating  or  cooling  to 
existing  conditions.  A  different  type  or  arrangement  of  furnace 
equipment  may  decrease  labor,  fuel  and  time;  utilize  the  floor 
space  to  better  advantage;  and  provide  more  comfortable  working 
conditions.  This  generally  results  in  an  increased  output  and 
lowered  production  cost  even  with  the  same  unit  prices  for  fuel, 
labor  and  power,  and  without  necessarily  requiring  new  building 
construction. 

Requirements  for  quality  should  determine  the  method 
of  heat  application.  With  this  as  a  basis,  the  production 
requirements  and  plant  conditions  should  determine  the  type, 
size,  number  and  arrangement  of  furnaces;  the  form  of  fuel  or 
electrical  energy;  and  the  methods  of  routing  and  handling  the 
material. 

It  is  a  common  but  misleading  assumption  that  control  of 
chamber  temperature  or  of  heat  supply  is  synonymous  with 
control  of  heated  product.  On  the  contrary,  control  of  the 
generation  of  heat  is  not  equivalent  to  control  of  the 
application  of  heat,  or  to  control  of  the  uniformity  of 
product.  Other  essential  factors  (page  13)  influence  the 
ultimate  result. 

The  difference  between  control  of  heat  as  it  is  generated 
in  the  furnace,  and  control  of  heat  as  it  is  applied  to  the 
product  in  the  furnace,  must  be  considered  with  electric  as  well 
as  fuel-fired  furnaces. 

The  comparative  ease  of  controlling  electricity,  gas  or  oil  is 
frequently  considered  as  the  determinative  factor  in  the  selection 
of  heating  equipment,  regardless  of  a  material  difference  in  price 
of  other  forms  of  heat  energy  or  equipment. 

Automatic  control  of  the  delivery  of  coal  through  stokers  or 
in  powdered  form;  of  gas,  oil  or  steam  through  automatic  valves; 
or  of  electricity  through  various  forms  of  regulating  devices, 
may  result  in  control  of  the  generation  of  heat,  but  does 
not  necessarily  determine  the  use  made  of  the  heat. 

The  question  of  control  involves  control  of  the  supply  of 
fuel  or  electricity  to  the  furnace;  control  of  supply  of  heat 
to  the  working  chamber;  control  of  the  heat  as  it  is  actually 
applied  to  the  surface  of  the  product;  and  control  of  the 


time  of  exposure  and  the  rate  at  which  heat  is  transferred 
to  the  product. 

Temperature  is  inseparably  linked  with  time  of  exposure 
and  rate  of  heating.  The  time  factor  must  be  considered  with 
reference  to  the  mass,  surface  and  shape  of  the  individual  piece; 
the  method  of  loading;  and  the  rate  at  which  heat  SHOULD  be 
transferred,  as  well  as  the  rate  at  which  heat  CAN  be  transferred 
to  effect  economy  in  fuel  or  time  of  heating. 

The  variable  factors  affecting  time  of  heating,  noted  on  the 
chart,  page  8,  indicate  the  necessity  of  considering  the  time  factor 
with  regard  to  the  result  sought  in  quality  of  the  finished  product. 
The  mass,  surface,  shape  or  section  of  the  charge  may  suggest  a 
slower  rate  of  heating,  from  the  viewpoint  of  the  metallurgist  or 
chemist,  with  regard  to  quality,  than  that  possible  from  the 
standpoint  of  the  engineer  to  increase  output  or  effect  economy 
in  fuel. 

The  influence  of  furnace  design  upon  the  application  and 
utilization  of  heat  is  far-reaching.  For  instance,  there  is  a 
radical  difference  between  the  arc,  induction,  and  resistance 
methods  of  generating  heat  by  electricity.  There  is  even  a 
distinction  within  each  of  these  broad  groups.  With  the  re- 
sistance method,  for  example,  the  heat  may  be  generated  by 
means  of  metallic  resistors  distributed  on  the  walls  of  the  furnace 
or  by  other  forms  of  resistance  material  the  nature  of  which 
prohibit  such  distribution.  In  each  instance  the  furnace  design 
must  be  adapted  to  the  method  of  generating  and  delivering  heat 
to  the  working  chamber. 

It  is  thus  apparent  that  the  practice  of  associating  a  given 
form  of  fuel  or  electricity  with  quality  or  low  cost  of  pro- 
duction is  misleading,  unless  there  is  definite  reference 
to  the  form  of  furnace  and  method  of  heat  application  and 
utilization. 

This  fact  may  be  illustrated  by  an  unusual  case  which  involved 
a  comparatively  efficient  type  of  furnace  fired  manually  with  bi- 
tuminous coal,  and  three  less  efficient  furnaces,  one  fired  with  oil, 
another  with  natural  gas  and  the  third  heated  electrically  through 
metallic  resistors  with  suitable  control  devices.  With  all  other 
conditions  substantially  alike,  it  was  conclusively  proved 
that  the  quality  and  cost  of  the  product  were  most  favor- 
able with  the  coal-fired  furnace. 

This  example,  however,  does  not  prove  that  any  one  method  of 
generating  heat  is  superior.  In  this  instance  the  difference  in 
results  was  due  to  the  better  design  and  operation  of  the 
coal-fired  furnace,  and  the  manner  of  applying  and  utilizing 
heat  in  the  product.  In  one  case,  the  apparent  disadvantage  of  a 
crude  form  of  fuel  was  overcome  by  an  efficient  furnace,  while  in 
the  others,  the  apparent  advantages  of  the  more  flexible  forms  of 
fuel,  and  particularly  the  advantage  of  electricity  with  control 
devices,  were  neutralized  by  inefficient  furnaces. 

Other  heat-treatment  processes,  manufacturing  requirements 
or  plant  conditions  might  prohibit  any  three  of  these  methods  of 
generating  heat;  and  the  most  expensive  form  of  heat  energy  in 
combination  with  a  suitable  furnace  might  show  better  results  at 
less  cost. 

There  is  no  one  form  of  fuel,  electricity  or  furnace  suit- 
able for  all  conditions — but  there  undoubtedly  is  a  suitable 
combination  which,  when  properly  used,  will  best  meet  the  re- 
quirements of  each  case. 

Cost  of  production  cannot  be  definitely  expressed  in  terms  of 
.output  per  operative,  per  unit  of  fuel,  time  or  floor  space.  It  is 
actually  determined  by  quality  and  ultimate  cost,  which 
include  many  intangible  factors  difficult  to  measure.  It  is  greatly 
influenced  by  the  nature  of  equipment  and  the  skill  and  in- 
telligence of  the  operatives.  Improvement  will  begin  with  proper 
selection  and  use  of  furnace  equipment  properly  adapted  to  the 
heat-treating  process,  manufacturing  requirements,  and  plant 
conditions. 


10 


INFLUENCE  OF   FURNACE   DESIGN   ON   COST  OF  PRODUCTION 

EXAMPLES     FROM      PRACTICE.      ILLUSTRATING     THE      ECONOMY      EFFECTED 
PROPER      SELECT.ON       AND       USE       OF       FURNACES      OF     1MPROVH 
D-12  ADAPTED      TO      MANUFACTURE       REQU.REMENTS     AND     ^AN?     CONDONS 


SMftLL  DROP  FORQE  FURNflCE  OPERATION 

J 

OUTPUT   PER   UNIT  OF   FLOOR  SPflCE -37J&  INCREflSE 
OUTPUT  PER    UNIT  OF  FUEL-7e«f0  INCREflSE 


SMflLL  DROP  FORQE  FURNflCE  OPERflTION 

OUTPUT  PER    UNIT  OF   FLOOR  SPflCE-  STT5y0  INCREflSE 
OUTPUT  PER  UNIT  OF  FUEL-  ZT^o  INCREflSE 


HEflT-TREflTINQ  DROP  FORQED  5TEEL  PflRTS 


OUTPUT  PER   MflN-IOOj&  INCREflSE 

EH 

OUTPUT  PER    UNIT    OF  FLOOR   SPflCE -I7fo     INCREflSE 

cn 

OUTPUT  PER    UNIT  OF   FUEL  -  33  J&  INCREASE 


CflRBONIZINQ  fiUTOMOBILE  PflRTS 


KJVW 

1700 
IfeOO 
1500 
1400 
1300 
1200 
1100 
1000 

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(*-!«»  HOURS   FIRINQ  TIME    FOR   FURNflCE"fl" 
1*23       «              »             H          u               M         "6" 
•^MRTERIRL     CHflRQED 

TEMPERflTURE  f  TIME  OF  HEflTINQ    PERIOD 
FURNflCE  "fl" 


5MRLL  DROP  FORQE  FURfNflCE  OPERflTION 

UNIT   OF    FLOOR     SPflCE  -eSOf.  INCRCR8C 
OUTPUT  PER  UNIT  OF  FUEL -47%  INCREflSE 


DROP  FORQE  FURNflCE  OPERflTION 


TIME  FROM  UQHTINQ    FURNflCE   TO  STflRTINQ    FORQINQ 
DCCREfWE 


OUTPUT    PER    HOUR  -43fo  INCREflSE 
OUTPUT    PER    UNIT  OF  FUEL -^0%  INCREASE 


HflRDENINQ  SNIflLL  HIQH  CflRBON  STEEL  PflRTS 

OUTPUT    PER  MflN- I40^>  INCREflSE 

OUTPUT   PER   UNIT   OF    FLOOR   SPflCE  -  50fo  INCREflSE 
I  1 

QUflLITy- REJECTIONS    REDUCED    FROM  Sfo  TO  .07fcf. 

flNNEflLINQ  PRESSED  STEEL  PflRTS 

OUTPUT    PER   MflN-75%  INCREflSE 

OUTPUT    PER  UNIT  OF    FLOOR   SPflCE  -  103  %  INCREASE 

cn 

OUTPUT  PER  UNIT   OF   FUEL-Z5%  INCREflSE 


flUTOMflTIC  END  flNNEflLINQ  OF  SMflLL  BRflSS  TUBES 

OUTPUT  PER  MRN- 200^0   INCREflSE 

CD 

OUTPUT    PER  UNIT  OF  FLOOR  SPflCE -O%  INCREflSE 
QUflLITy-  REJECTIONS    REDUCED  FROM   5^«  TO  If* 

flUTOMflTIC  END  flNNEflLINQ  OF  LflRQE  BRflSS  TUBES 

OUTPUT   PER  MflN- 275^0  INCREflSE 

OUTPUT    PER  UNIT  OF   FLOOR   SPflCE  -28Of»  INCREflSE 


B"  -  4  FOR   SflME    OUTPUT  QUflLlTy-  REJECTIONS    REDUCED    FROM    10%  TO  I  % 

iMH^M  i^^HH  ••••1 


r  ur\  nrn-c.     o        ~T   r  wrv    w»  ii  ii*    ** 

_  DDDD 

EQUIVflLENT    MEflRTH   flREfl,-  FLOOR  SPflCE 
flND    RELflTIVE    WflLL  THICKNESS 


CMEMICflL  OXlDflTION  OF  METflLLIC   POWDER 

OUTPUT    PER   MflN-6>5O"fo  INCREflSE 

OUTPUT  PER  UNIT    OF   FLOOR   SPflCE  -II  10  "f»  INCREflSE 


I ^Ml 

OUTPUT    PER   UNIT  OF  FUEL  -<^0  fo  INCREflSE    WITH 
FMRNftCE  "fl"   OVER    FURNflCES  "B" 


-OXIOflT  I  ON    INCREftSED    FROM  &O%  TO 


Fig.  5 


11 


««• 


Selection   of  Furnaces 


HE  selection  of  industrial  heating  equipment, 
which  must  be  coincident  with  the  selection  of  a. 
suitable  form  of  heat  energy  (combustible  or  elec- 
tric), resolves  itself  into  the  problem  of  determin- 
ing the  type,  design,  size,  number  and  arrange- 
ment of  furnaces  and  auxiliary  equipment  necessary 
to  meet  specific  plant  conditions,  and  of  providing  the  most 
efficient  methods  of  heating,  cooling,  routing  and  handling  the 
material. 

The  physical  or  chemical  nature  of  the  heat-treatment 
process;  the  requirements  of  quality;  rate  and  quantity  of 
production;  plant  conditions  and  cost  of  operation  are 
basic  factors  which  influence  selection.  There  are  many 
other  factors  of  varying  importance,  outlined  by  the  chart  on 
page  13,  any  one  of  which  may  also  influence  the  selection 
and  arrangement  of  equipment  or  the  cost  of  production. 

Uniformity  of  heating  and  cooling,  and  the  relationship 
of  temperature,  atmosphere,  rate  and  time  of  heating  and  cooling 
to  the  surface  exposure  and  mass  of  product,  are  governed  by 
natural  laws  which  cannot  be  ignored  without  sacrifice  in  quality 
or  quantity  of  product  or  economy  of  operation. 

Selection  is  largely  a  matter  of  compromise  in  reconciling 
requirements  of  quality  with  others  related  to  methods  of  heating 
and  handling,  output,  plant  conditions  and  cost  of  production. 

Standardization  of  furnaces  as  to  type,  design  and  size, 
to  the  extent  common  with  boilers,  engines,  motors,  machine 
tools,  etc.,  is  impracticable  because  of  the  endless  variety  of 
individual  requirements.  Such  requirements  usually  involve 
differences  in  size,  shape,  weight  or  composition  of  materials; 
quantity  and  rate  of  flow;  processes;  methods  of  heating,  cooling, 
routing  and  handling  of  material;  arrangement  of  equipment; 
floor  space;  hours  of  operation;  forms  of  fuel  available;  etc. 
To  meet  such  conditions  there  must  be  corresponding 
variety  in  design  and  size  of  furnaces. 

There  is  no  more  reason  to  assume  that  one  form  of  fuel, 
electricity,  or  furnace  may  be  adapted  to  all  industrial  heating 
requirements,  than  to  assume  that  one  type  of  dwelling  or  factory 
would  meet  all  building  requirements,  or  that  one  form  of  prime 
mover  would  meet  all  requirements  for  power. 

The  difficulty  of  definitely  measuring  heating  results, 
unlike  measuring  results  in  power,  illumination  or  transportation, 
adds  to  the  complication  because  appraisement  of  furnace 
performance  must  be  based  on  quality  and  cost  of  prod- 
uct and  the  method  of  operation  under  specific  plant 
conditions. 

Temperature  control,  price  or  quantity  of  fuel,  composition 
of  gases,  etc.,  are  merely  contributing  factors,  and  bear  about  the 
same  relation  to  industrial  heating  as  they  bear  to  the  operation 
of  a  motor  truck. 

The  "heat  unit"  (B.  t.  u.)  standard  for  judging  fuel 
values  and  "  heat  balance  "  for  testing  furnace  performance 
are  incomplete  and  misleading,  except  for  comparing  fuels 
of  the  same  physical  and  chemical  characteristics,  and  furnaces 
of  the  same  mechanical  characteristics,  operated  under  identical 
conditions  of  applying  and  utilizing  heat  and  of  loading  and 
handling  material.  The  "heat  unit  value"  of  a  fuel,  like  the 
"heat  balance"  of  a  furnace,  is  but  one  indication  of  economic 
value. 

It  is  misleading  to  compare  coal,  oil,  gas  or  electricity 
without  considering  their  form  characteristics  and  the 
differences  in  the  mechanical  form  and  operation  of  the 
furnaces  or  other  appliances  adapted  to  their  use.  Like- 
wise, it  is  misleading  to  compare  fuels  of  the  same  physical  form, 


such  as  clean  producer  gas,  water  gas,  city  gas,  natural  gas, 
acetylene  gas,  etc.,  without  considering  differences  in  chemical 
composition,  combustible  mixture,  products  of  combustion  and 
calorific  intensity  of  heat  release.  Consideration  must  be 
given  to  the  influence  of  furnace  design  and  operation 
upon  the  temperature  and  atmosphere,  and  upon  the 
uniformity  and  cost  of  product. 

Electricity  must  be  considered  with  regard  to  its  "form 
value"  in  determining  its  field  of  usefulness.  A  difference 
in  current  (alternating  or  direct),  or  in  voltage,  phase  or  cycle; 
the  difference  between  arc,  resistance  and  induction  methods  of 
releasing  heat,  and  the  effect  upon  the  product  of  differences  in 
the  atmosphere  set  up  in  releasing  the  heat,  must  be  considered  in 
relation  to  individual  requirements. 

The  common  practice  of  comparing  inefficient  furnaces, 

unsuited  to  the  specific  manufacturing  conditions  and  improperly 
operated,  with  furnaces  of  a  suitable  type,  more  efficiently 
operated,  using  another  form  of  fuel,  and  crediting  the  improved 
results  to  the  difference  in  form  of  fuel  or  heat  energy,  is  largely 
responsible  for  mistakes  in  the  selection  of  both  furnaces  and 
fuels. 

The  "form  value"  of  fuel  or  heat  energy  must  be  con- 
sidered with  the  design  and  operation  of  the  furnace. 

Very  often  a  fuel  requires  a  particular  type  of  furnace  to  enable  it 
to  do  certain  work.  Producer  gas,  for  instance,  is  unsuited  for 
melting  steel  except  in  a  regenerative  furnace.  Electricity  with 
the  resistance  method  of  releasing  heat  may  be  used  to  accomplish 
a  result  not  possible  with  the  arc  method,  or  vice  versa. 

It  is  unreasonable  to  compare  an  intermittently  operated  or 
"batch  type"  regenerative  furnace  with  a  furnace  of  the  con- 
tinuous non-regenerative  type,  or  to  compare  continuous  furnaces 
of  different  types,  or  single-chamber  with  multi-chamber  furnaces, 
even  though  the  "heat  balance"  be  identical,  unless  each  affords 
equally  efficient  means  for  applying  the  heat  and  handling  the 
product. 

A  difference  in  method  of  applying  heat  or  handling 
material  may  result  in  a  difference  in  quality  or  cost  of 
product  that  would  not  be  disclosed  by  consideration  solely  of 
heat  balance,  fuel  consumption,  analysis  of  flue  gases  or  indica- 
tion of  chamber  temperature  control. 

No  one  type  of  furnace  or  form  of  heat  energy  (com- 
bustible or  electric)  has  a  monopoly  on  uniformity  of 
heating  or  economy  of  operation. 

Furnaces  and  fuels  should  be  selected  for  the  useful  service 
they  can  render  when  properly  employed  under  specific  condi- 
tions, and  with  due  regard  to  their  form  as  well  as  price.  Each 
should  be  selected  on  its  merits,  judged  by  the  factors  outlined  in 
the  chart.  Their  use  is  but  a  means  to  an  end,  the  economic 
value  of  which  is  measured  by  the  resulting  quality  and  cost 
of  the  finished  product  or  service,  and  not  by  any  one  phase 
of  their  performance. 

The  variety  in  furnace  design  is  illustrated  by  the  accom- 
panying diagrams  of  Rockwell  furnaces,  which  have  been  developed 
during  many  years  of  practice  in  different  branches  of  industry. 
Virtually  all  of  the  furnaces  illustrated,  each  of  which  has  its 
field  of  usefulness  as  well  as  its  limitations,  have  been  built  in 
different  sizes  with  varying  methods  of  heat  application,  arrange- 
ment of  chambers,  working  openings,  etc.,  for  the  use  of  different 
fuels  and  electricity,  to  meet  a  wide  range  of  heating  processes, 
manufacturing  requirements  and  plant  conditions.  They 
illustrate  the  endless  variety  of  methods  of  applying  in  practice 
the  principles  that  govern  the  production  of  heat-treated  prod- 
ucts, and  the  necessity  for  considering  each  case  on  its  merits 
and  in  light  of  the  development  resulting  from  practice. 


12 


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13 


HEATING     FURNACES 

LIGHT    AND    HEAVY    FORGING    -    WELDING    -    TUBE    BRAZING    -    RIVET.  PLATE.  ANGLE    AND    BILLET    HEATING   - 

CONTINUOUS    SLUG.    BILLET    AND    ROD    HEATING 


u 


2  -  FB  3  -  FC  4  -   FD  5  -  FE 


6  -  FF  7   -  fG  6  -  FH  9   -  FJ    '  10  -  FK 


17  -  FR  -  18  -  FS 


-      21  -  FV  22-  FW  23-  FX  24-  FY  25-  FZ  26-  HA 


Fig.  7 


14 


ANNEALING  AND  HEAT-TREATING  FURNACES 

HARDENING     -    TEMPERING    -    CARBON.ZING     -    SHEET.     ROD.    W.RE    AND    TUBE     MILL    ANNEALING 

SPRING    FITTING    -    HIGH    SPEED    STEEL    HARDENING 


Fi 


15 


ANNEALING    AND    HEAT-TREATING    FURNACES 

SHEET,    ROD.    WIRE    AND    TUBE    MILL    ANNEALING    -    CIRCULAR    SAW    AND    PLATE    HARDENING   WITH 

PREHEATING    CHAMBER    —  PUSHER.    PAN    PULLER    AND    CONTINUOUS    LIVE    ROLL    ANNEALING 

AND    HEAT-TREATING    -    PACK    ANNEALING    IN    TUBES    WITH    CHARGING    TRUCK 


73 


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Fig.  9 


16 


CAR-AND-BALL    AND    CAR    TYPE    FURNACES 

DRY.NG    -    BAK.NG    -    BLU.NG    -    JAPANN.NG   _  CORE    QVENS    .   HEAT.TREAT)NG 

LARGE    .RREGULAR    FORG.NGS    AND    CAST,NGS    -    MISCELLANEOUS    MATER.AL 
PACKED    IN    POTS    OR    BOXES    FOR    BRIGHT    ANNEALING.    ETC. 


J 


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Fi?.  10 


17 


CONTINUOUS    ANNEALING    AND    HEAT-TREATING    FURNACES 


£&M«lur£TO 


PUSHER    TYPES    FOR    ANNEALING    SMALL    PARTS    IN    PANS.    WITH    COOLING    TABLE.    MECHANICAL    DUMP    INTO 

PICKLING    MACHINE    OR    TRUCK.   WITH    CONVEYOR    RETURN   OF   PANS   TO   CHARGING    END   -   CONVEYOR 

AND     PUSHER    TYPES    FOR    A    SEQUENCE    OF    HEATING    AND    COOLING    OPERATIONS 


Fig.  11 


18 


AUTOMATIC    CONVEYOR    FURNACES 

CARRY-THROUGH.    .NS.DE    DISCHARGE   AND   SIDE   TAKE-OUT  TYPES   FOR   DRY.NG.   ANNEAL.NG.   HARDENING    AND 
TEMPERING    -    ALSO    FOR    VERTICAL    AND    HORIZONTAL    END    HEATING    AND    FOR    STR.P    ANNEALING 


I 


AV  V\    \VA\   AY  VYAVAVAVA 


ffi 


Fig.  1 


19 


MUFFLE,    RETORT    AND    POT    FURNACES 

DIRECT-FIRED    AND    MUFFLE    TYPES    FOR    ENAMELING,    CUPELLING.    RETORT  ANNEALING   AND   HEAT-TREATING  — 

AIR   AND   GAS   HEATING    -   GALVANIZING   AND   TINNING   -   CYANIDE,    LEAD.   SALT   AND   OIL   BATHS   -   SOFT 

METAL    MELTING    -    MISCELLANEOUS    CHEMICAL,    LIQUID    BOILING    AND    SIMILAR    OPERATIONS 


tO-EK 


Fig.  13 


20 


CONTINUOUS    ANNEALING    AND    HEAT-TREATING    FURNACES 

BRIGHT    ANNEALING    FOR    COPPER    -    OIL    AND    LEAD    TEMPERING    -    WIRE    PATENTING    -    TINNING    FOR 
STRIP.    WIRE    AND    SHEET    -    HARDENING    AND    TEMPERING    IN    SEQUENCE    - 
OPEN    FLAME    AND    PLATE    TYPE    CLOTH    SINGEING 


\ 


Fig 


21 


ANNEALING,  HEAT-TREATING  AND  PROCESSING   FURNACES 

DRYING  -  PLATE  AND  SAW  TEMPERING  IN  SHAPE-RETAINING   DIES  -   ROTATING  HEARTH  TYPES,  WITH  MANUAL3 

OR  AUTOMATIC   SIDE  OR  CENTER   DISCHARGE  -  ROTARY    CARBONIZING  -  REVOLVING   DRUM,  SCREW 

CONVEYOR    AND    RABBLING    TYPES    FOR    PROCESSING     -     REMOVABLE    ROOF    TYPE    FOR 

ANNEALING,  HARDENING,  TEMPERING  AND  SHRINKING  -  LIVE  ROLL  TIRE  HEATING 


Fig.  15 


22 


ROTARY    CYLINDRICAL    FURNACES 


INTERNALLY  AND   EXTERNALLY   FIRED  TYPES   FOR  ANNEALING   AND  HEAT-TREATING   BOLTS.   RIVETS.   FORCINGS 
CUPS.    HUBS    AND    OTHER    MISCELLANEOUS    MATERIAL    -    DRYING.    OXIDIZING    AND    REDUCING 
METALLIC    AND    MINERAL    POWDERS    -    HEAT-TREATING    OPERATIONS    IN    SEQUENCE 


23 


AUTOMATIC    HEAT-TREATING    FURNACE    ARRANGEMENTS 

ROTARY  CYLINDRICAL  TYPE  IN  SERIES  FOR  A  THREE-OPERATION  HEAT-TREATMENT,  WITH  MECHANICAL  TRANSFER  - 

CARRY-THROUGH    AND    INSIDE    DISCHARGE    WALKING    BEAM    TYPES    FOR    ANNEALING    AND    HEAT-TREATING  - 

FLOOR  PLAN  OF  CONVEYOR    FURNACES  IN  COMBINATION  WITH  FORMING  MACHINE  AND  QUENCHING  TANK 


'V.'V .''/////// ////TV. 


—  5  -  BE 


Fig.  17 


24 


MELTING    FURNACES 

SCRAP    RECLAIMING    -    VITREOUS    ENAMEL    MELTING    -    PRECIOUS    AND    NON-FERROUS    METAL    MELTING    IN 
STATIONARY    AND    TILTING    CRUCIBLE    AND    REVERBERATORY    TYPES 


25 


Scope  and  Limitations  of  Regenerative  Furnaces 


HE  regenerative  furnace  illustrates  the  neces- 
sity of  considering  the  suitability  of  type  and 
design  of  furnace  and  form  of  heat  energy  (com- 
bustible or  electric)  and  the  relation  of  thermal 
conditions  incident  to  the  generation  or 
utilization  of  heat  in  a  furnace  to  other 

equally  essential  factors  that  influence  the  quality  and  cost 

of  heat-treated  products. 

Like  the  thermally  efficient  gas  or  oil  engine,  the  re- 
generative furnace  has  its  limitations  as  well  as  its  field  of 
usefulness.  It  is  an  efficient  type  of  furnace  for  releasing  and 
utilizing  heat  from  fuel,  and  is  particularly  suitable  for  the  use  of 
fuels,  such  as  producer  gas,  which,  by  reason  of  chemical  compo- 
sition and  low  calorific  intensity,  are  not  suited  to  high  temper- 
ature heating  requirements  without  regeneration. 

The  regenerative  principle,  by  recovering  a  part  of  the  sensible 
heat  carried  out  of  the  heating  chamber  by  the  spent  gases, 
and  utilizing  it  to  preheat  the  air  or  fuel,  or  both,  permits  a  high 
ruling  temperature  and  results  in  economy  of  fuel. 

The  regenerative  furnace  should  be  considered  when  the  tem- 
perature and  nature  of  the  heating  process,  the  size  of  the  furnace, 
the  cycle  of  operation  or  the  plant  conditions  will  not  permit  of  a 
simpler  or  cheaper  method  of  securing  the  result  desired. 

Regeneration,  like  recuperation,  is  really  an  indirect 
method  of  utilizing  or  recovering  heat,  and  at  times  is 
limited  to  preheating  the  air  alone,  as  certain  fuels,  such  as  natural 
gas  and  other  hydrocarbon  gases,  cannot  be  preheated  to  the^ 
extent  possible  with  producer  gas.  When  the  temperature 
requirements  and  plant  conditions  permit  the  use  of 
furnaces  with  more  direct  methods  of  utilization  or  re- 
covery, the  regenerative  principle  is  unnecessary.  But 
where  a  high  temperature  is  required,  as  for  heavy  forging, 
welding  or  melting  operations,  it  is  frequently  necessary  to 
resort  to  regeneration  in  order  to  establish  a  sufficient  tem- 
perature differential,  to  increase  the  rate  of  heating,  or  to  make 
possible  the  attainment  of  the  desired  working  tempera- 
ture, regardless  of  the  saving  in  fuel  or  cost  of  furnace. 

Considerable  time  is  required  to  raise  the  temperature  in  the 
regenerative  furnace  from  a  comparatively  cold  condition  to  a 
relatively  high  working  temperature.  This  is  objectionable 
when  the  furnace  is  used  only  eight  or  ten  hours  per  day,  unless 
the  heat  is  maintained  between  shifts  to  balance  radiation  and 
flue  losses.  Temperature  requirements  and  the  nature  of  the 
heating  process  or  of  the  fuel  may,  however,  make  this  fornace 
and  practice  desirable  even  under  such  intermittent  operation. 
The  objection  does  not  hold  when  the  furnace  is  operated  con- 
tinually at  working  temperature  and  capacity  in  two  or  more 
shifts. 

Practically  all  regenerative  furnaces  are  of  the  "batch" 
type  and,  therefore,  limited  in  ability  to  continually  maintain  the 
chamber  at  full  working  capacity  and  at  uniform  temperature, 
due  to  the  "batch"  method  of  charging  and  discharging. 

The  requirements  of  temperature,  output  and  the  nature  of  a 
process,  such  as  melting,  may  make  this  batch  handling  necessary. 


In  other  operations  not  confined  to  the  "batch"  type  furnace, 
an  increase  in  production  requirements  without  a  change  in  the 
nature  of  the  heating  process  may  suggest  a  different  type  of 
furnace,  capable  of  showing  equal  fuel  economy  with  added 
advantages  in  the  metrfod  of  applying  and  utilizing  heat,  handling 
material,  reduction  in  floor  space,  etc. 

Regeneration  should  not  be  considered  when  the  furnaces 
required  are  comparatively  small  and  scattered.  The  floor 
space  required  for  a  regenerative  furnace  is  relatively  large,  due 
to  the  area  of  the  regenerators,  reversing  valves,  flues  and 
chimney,  which  frequently  occupy  a  greater  space  than  the 
furnace  itself.  This,  with  the  heavier  foundations  required, 
must  be  considered  with  the  production  requirements,  plant 
conditions  and  the  space  available  for  the  furnaces,  machines  and 
operatives. 

There  is  a  limit  in  the  size  of  a  regenerative  furnace* 
below  which  it  is  impracticable  to  go,  because  the  possible 
economy  in  fuel  is  outweighed  by  other  considerations  related  to 
the  cost  of  installation  and  operation. 

The  regenerative  furnaces  of  Rockwell  design  illustrated  on 
page  27,  all  of  which  were  built  prior  to  1900,  compare  favorably 
with  the  best  present-day  practice. 

From  the  standpoint  of  fuel  economy,  these  furnaces  were 
entitled  to  consideration  prior  to  1900  just  as  they  are  today. 
Conditions  limited  their  use  at  that  time  just  as  conditions,  of  a 
different  nature,  limit  their  use  now. 

The  tendency  to  consider  the  regenerative  or  recupera- 
tive furnace  as  a  possible  solution  of  the  so-called  "fuel 
problem"  should  lead  to  consideration  of  conditions  responsible 
for  the  limited  use  of  such  furnaces  in  the  past  and  the  extent  of 
their  use  in  the  future. 

The  relative  cheapness  in  the  past  and  flexibility  of  such  highly 
concentrated  fuels  as  natural  gas  and  oil  made  it  possible  for 
the  manufacturer  to  conduct  many  of  his  heating  operations 
without  regard  to  fuel  conservation.  As  fuel  was  cheap  and 
apparently  not  worth  saving,  the  regenerative  furnace  did  not 
often  appeal  to  him.  Production,  rather  than  cost  of  fuel,  was 
the  order  of  the  day.  This,  with  relatively  low  labor  cost  and 
working  conditions  not  now  countenanced,  have  been  responsible 
for  the  lack  of  progress  that  should  have  followed  as  a  matter  of 
course. 

Changing  conditions  and  the  demand  for  better  quality 
and  decreased  cost,  coupled  with  relatively  higher  prices  for 
material,  fuel  and  labor,  will  compel  an  increasing  apprecia- 
tion of  all  the  factors  that  control  the  selection  and  use  of 
furnaces  and  fuels  for  the  production  of  heat-treated  products. 

The  question  is  not  merely  one  of  building  a  furnace 
properly,  but  of  determining  the  proper  type  and  Design  of 
furnace  to  be  built,  with  due  regard  to  its  suitability  to  the 
nature  of  the  heating  operation,  the  manufacturing  requirements 
and  the  plant  conditions.  This  calls  for  a  careful  study  of  the 
problem  as  a  whole,  in  order  that  none  of  the  essential  factors 
affecting  the  quality  of  product  and  the  cost  of  production 
in  the  plant  may  be  overlooked  in  an  abstract  consideration  of  the 
generation  and  utilization  of  heat  in  a  furnace. 


26 


REGENERATIVE    FURNACES 


FORGING    -    WELDING    -    ROLLING    - 
CRUCIBLE    PIT    MELTING 


27 


Relation  of  Type  and  Arrangement  of  Equipment 

to  Cost  of  Production 


NE  of  the  prime  necessities  when  selecting  in- 
dustrial heating  equipment  is  to  provide  means 
for  such  heat  application  to  the  material 
as  will  produce  the  best  quality  of  finished 
product.  It  is  'equally  necessary  to  provide 
equipment  of  such  nature,  extent  and  arrange- 
ment as  will  afford  the  best  means  for  handling  as  well  as 
heating  the  material  in  order  to  produce  the  greatest  quantity 
at  the  lowest  cost.  And  it  is  certainly  advantageous  to  provide 
means  for  the  operatives  to  work  efficiently  and  in 
reasonable  comfort. 

All  these  considerations  should  contribute  to  the  final  result, 
so  that  the  required  quality  and  quantity  of  finished  product  may 
be  secured  with  minimum  labor,  fuel,  power,  floor  space,  rejected 
material  and  overhead  charges. 

The  advantages  of  adapting  industrial  heating  equip- 
ment to  the  manufacturing  requirements  and  plant  con- 
ditions in  each  individual  case  are  not  always  appreciated. 
Consideration  only  of  strictly  thermal  features  of  the  operation 
is  often  responsible  for  failure  to  effect  the  economies  which, 
almost  without  exception,  may  be  brought  about  by  intelligent 
selection,  arrangement  and  operation  of  equipment 
properly  adapted  to  the  individual  plant  conditions. 

No  two  cases  are  alike.  Two  plants  manufacturing  the 
same  product  in  the  same  quantity  may  require  different  heating 
equipment  or  different  fuel,  just  as  they  may  require  different 
building  construction  or  different  methods  of  handling  the  mate- 
rial. Two  separate  departments  of  the  same  plant  working  on  the 
same  material  may  require  different  equipment,  fuel  or  methods 
on  account  of  different  manufacturing  requirements  or  other 
influences  such  as  location,  floor  space,  relation  of  these  to  each 
other,  etc. 

A  different  and  better  type  of  furnace,  a  different  ar- 
rangement of  furnaces  or  other  equipment,  method  of 
handling,  form  of  fuel  or  all  together  may  so  alter  an 
overcrowded,  uncomfortable  heating  department  that  it 
will  turn  out  more  and  better  product  at  less  cost. 

The  furnace  floor  plans  on  page  29  (without  reference  to  size 
of  furnace  or  manner  of  heating)  illustrate  different  arrangements 
of  chambers  and  working  openings,  and  suggest  different  types 
and  designs  of  furnaces  and  various  methods  of  charging  and 
discharging  in  order  to  secure  the  greatest  uniformity  of  product 
and  rate  of  production. 

i 
"  1-KA"  may  be  a  tool  room  forge  with  a  chamber  a  few  inches 

wide  or  a  plate  heating  furnace  fifteen  or  twenty  feet  wide. 
Or  it  may  vary  in  length  from  a  size  required  to  heat  a  small  tool 
up  to  one  suitable  for  a  steel  shaft  a  hundred  feet  long.  It  may 
represent  the  chamber  in  a  japanning  oven  maintaining  heat  at  a 
few  hundred  degrees  or  a  furnace  for  forging  steel. 


"25-KZ"  similarly  may  vary  in  chamber  size  and  temperature, 
with  means  for  moving  the  material  through  the  chamber  con- 
tinuously or  intermittently,  or  for  charging  and  discharging  at 
either  or  both  ends. 

Either  of  these  may  be  built  in  double-chamber  form  (7-KG  or 
29-LD)  with  similar  variations  in  size  or  temperature,  and  various 
methods  pf  handling  material  and  producing  and  applying  heat. 

Many  such  combinations  may  be  provided  to  facilitate 
the  proper  heating  and  handling  of  the  material.  Other 
combinations  may  be  warranted  by  the  necessity  for  improve- 
ment in  working  conditions,  to  employ  the  floor  space  to  better 
advantage,  or  to  effect  the  general  all-around  economy  that 
frequently  results  from  discarding  comparatively  small  and  in- 
efficient furnaces  in  favor  of  the  larger  and  heavier  units. 

The  type,  design,  size  and  .number  of  furnaces,  with  reference  to 
the  form  and  calorific  intensity  of  the  fuel  or  heat  energy,  and  the 
methods  of  handling  and  routing  material  must  be  determined 
with  reference  to  the  methods  of  heat  application,  manufacturing 
requirements  and  plant  conditions.  The  furnace  units  should 
be  as  few  as  possible  to  secure  the  desired  output  with 
continuity  of  operation.  Each  should  be  properly  designed 
and  proportioned  so  that  it  will  contribute  its  share  of  properly 
he'ated  product  with  economy  of  fuel,  labor  and  floor  space. 

A  number  of  small  furnaces  should  not  be  considered  when 
fewer  larger  units  may  be  employed,  because  of  the  relative  re- 
duction in  floor  space,  radiating  surface,  fuel  consumption,  time 
and  labor. 

Manufacturing  requirements  for  quality  product  at  low 
cost  under  conditions  of  quantity  production  frequently 
suggest  mechanical  means  for  handling  to  such  an  extent 
that  the  furnace  is  in  reality  an  automatic  heating 
machine. 

Such  automatic  methods  represent  ideal  practice  and  should  be 
chosen  wherever  the  conditions  permit.  The  field  of  usefulness 
of  such  automatic  methods,  however,  is  limited  by  the  quantity 
or  rate  of  flow  of  the  material  to  be  heat-treated,  and  by  varia- 
tions in  size,  shape  or  composition  of  the  individual  pieces  or 
batches,  and  by  other  conditions  that  do  not  permit  of  strictly 
continuous  operation  on  a  comparatively  large  scale. 

To  heat  correctly  is  the  first  consideration.  Whatever  the 
manner  of  heat  application  or  method  of  handling  material,  it 
must  always  be  borne  in  mind  that  the  fundamental  factors 
governing  uniformity  of  heating  or  cooling  cannot  be 
ignored  without  corresponding  sacrifice  in  quality  of  product 
and  ultimate  cost. 

To  heat  economically  it  is  necessary  to  consider  the  influence 
of  the  type,  design,  size,  number  and  arrangement  of  furnaces 
on  the  items  of  labor,  fuel,  output,  floor  space,  and  investment, 
and  other  items  included  in  the  actual  cost  of  production. 


28 


ARRANGEMENTS  OF  FURNACE  CHAMBERS  AND  WORKING  OPENINGS 

SOME    OF    THE    POSSIBLE    ARRANGEMENTS    OF    FURNACE    CHAMBERS    AND    WORKING    OPEN.NGS 

AVAILABLE    FOR    MEET.NG    .NDIV.DUAL    REQU.REMENTS    AS    TO    MATERIAL    TO    BE    HEATED. 

CHARACTER    OF    OPERATION    AND    PLANT    CONDITIONS 


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Fig.  20 


29 


Relation  of  Price  of  Fuel  to  Cost  of  Production 


HE  relation  of  price  of  fuel  to  ultimate  cost  of 
production  in  industrial  heating  is,  in  many 
respects,  similar  to  that  prevailing  under  other 
conditions  involving  the  use  of  fuel  or  heat,  such 
as  illumination  or  transportation. 

The  character  and  cost  of  the  final  result 
are  determined  by  a  combination  of  apparatus,  fuel  and 
operative,  and  not  by  any  one  or  two  of  these  factors. 

The  cost  of  fuel,  which  is  based  upon  the  price  and  quan- 
tity consumed,  is  but  one  item  in  the  ultimate  cost  of 
production.  The  fuel  consumption  is  governed  by  the 
design  of  the  furnace  and  the  manner  in  which  the  heat  is  gener- 
ated, applied  and  utilized.  The  average  manufacturer  does  not 
control  the  price  of  fuel,  but  to  a  great  extent  he  can  control  the 
cost  of  his  heating  operations  by  using  furnaces  and  fuels 
adapted  to  his  manufacturing  requirements  and  plant 
conditions. 

Too  great  emphasis  is  usually  placed  on  the  heat  unit 
(B.  t.  u.)  cost  of  fuel  and  upon  the  details  of  combustion 
and  heat  release ;  and  too  little  attention  is  given  to  the  economy 
attainable  under  better  methods  of  heat  application  and  utiliza- 
tion possible  with  apparatus  of  improved  design. 

The  practice  of  selecting  fuel  on  the  basis  of  "heat  unit 
cost, "  or  of  selecting  apparatus  to  use  any  one  form  of 
fuel  on  the  basis  of  "  heat  balance,  "  or  "fuel  consumption,  " 
without  considering  the  mechanical  form  and  suitability  of  the 
apparatus,  or  the  intelligence  and  skill  of  the  operatives,  is  just 
as  illogical  in  industrial  heating  as  in  transportation. 

Many  absurd  comparisons  are  made  between  different  fuels 
merely  on  their  heat  unit  content,  without  regard  to  physical  and 
chemical  form,  which  very  largely  determine  their  field  of  useful- 
ness. 

Price,  on  the  basis  of  heat  unit  content,  must  be  con- 
sidered together  with  the  form  of  fuel  and  apparatus,  and 

the  suitability  of  both  to  the  conditions. 

The  economic  value  due  to  "form"  of  fuel  and  equip- 
ment, suggests  consideration  of  "form  value"  in  the  selection 
of  fuels  and  furnaces  or  other  apparatus  dependent  upon  heat  for 
operation. 

"Form  value"  is  a  term  denoting  the  intangible  value  due 
to  physical  condition  or  chemical  association  of  a  source  of 
heat  energy  (combustible,  electrical  or  mechanical)  and  method 
(apparatus  and  operation)  of  transformation  into  useful  service. 
It  is  not  measured  by  the  thermal  (B.  t.  u.)  value  or  the  price 
of  fuel,  nor  the  type,  price  or  heat  balance  of  a  furnace. 

Innumerable  instances  in  the  fields  of  power  production, 
transportation,  and  illumination  indicate  that  "form  value"  is 
of  greater  importance  than  thermal  value  in  the  selection  of 
fuel  and  apparatus.  Otherwise  no  other  form  of  heat  energy 
could  compete  with  bituminous  coal,  and  the  chief  elements  of 
progress  in  each  field  thus  far  attained  would  be  nullified. 

"Form  value"  is  a  factor  of  fundamental  significance  in 
the  problem  of  selecting  fuels  and  furnaces  or  other 
apparatus  dependent  upon  heat  for  operation.  Accordingly, 
an  adequate  survey  of  the  problem  should  include  specific  con- 
sideration of  the  "form  value,"  in  addition  to  the  "thermal 
value, "  price  of  fuel,  "  heat  balance,  "  and  cost  of  apparatus. 

Such  survey  is  necessary  for  an  unbiased  consideration  of  the 
problem  as  a  whole  and  a  proper  appraisal  of  the  actual  require- 
ments. Individual  conditions  and  the  economic  value  of 
the  ultimate  result  must  decide  the  conflicting  claims  of  ad- 


vocates of  the  arc,  induction  or  resistance  methods  of  heating  by 
electricity;  combustion  experts;  those  urging  the  merits  of  differ- 
ent forms  of  gas  generated  in  isolated  or  central  station  plants; 
fuel  oil  or  powdered  coal  enthusiasts;  mechanical  stoker  adherents, 
etc.,  or  those  interested  in  special  forms  of  furnaces  or  other 
apparatus  without  reference  to  the  form  of  fuel  or  electricity 
to  be  employed  in  connection  with  them. 

The  approximate  relation  of  the  heat  energy  in  fuel  to 
the  results  accomplished  by  its  use,  and  the  possibilities  for 
improvement  in  application  and  utilization  of  such  heat  energy, 
are  illustrated  by  the  diagrams  on  page  31,  which  are  fairly 
representative  of  present-day  practice. 

The  indirect  relation  of  the  cost  of  fuel  and  the  more 
direct  relation  of  the  combination  of  equipment,  fuel  and 
operative  to  the  character  and  total  cost  of  the  service  or  prod- 
uct is  even  more  pronounced  in  industrial  heating  than  in  the  more 
highly  developed  field  of  power. 

Inadequate  appreciation  of  the  great  variety  of  manufacturing 
conditions;  the  difficulty  of  definitely  valuing  the  quality  and 
cost  of  finished  product ;  and  the  too  frequent  practice  of  apprais- 
ing the  operation  by  thermal  standards  only,  lead  to  neglect  of 
the  principles  governing  the  production  of  heat-treated  products 
and  the  selection  and  operation  of  apparatus  as  a  proper  means 
to  that  end. 

It  is  apparent  from  practice  that  unless  other  conditions 
are  equal,  the  cost  of  fuel  or  so-called  "thermal  efficiency" 
of  the  apparatus  are  not  the  determinative  factors. 

The  common  hot-air  engine  extensively  used  in  isolated  country 
districts  for  pumping  water,  and  for  other  operations  requiring  a 
small  amount  of  power,  is  relatively  inefficient  in  utilizing  fuel 
energy  compared  with  the  Diesel  or  other  internal  combustion 
engines.  Under  certain  conditions,  however,  it  has  some  operat- 
ing advantages  in  permitting  the  use  of  comparatively  cheap  fuel 
and  requiring  minimum  attention,  the  economic  value  of  which 
more  than  offset  the  loss  in  fuel. 

The  simply  constructed  and  operated  foundry  cupola  for 
melting  grey  iron  is  generally  considered  an  example  of  thermal 
inefficiency  compared  with  the  modern  regenerative  open  hearth 
furnace  for  melting  steel.  Although  the  two  should  not  be 
compared  on  the  basis  of  "heat  balance,"  because  of  the  differ- 
ence in  construction,  operation  and  purpose,  it  is  interesting  to 
note  that  the  cupola  is  the  more  efficient  of  the  two  in  heat  appli- 
cation to  the  product  and  in  utilization  of  heat.  If 
it  were  operated  continuously  and  the  waste  heat  utilized  as  in 
blast  furnace  practice,  the  comparison  would  be  even  more 
striking. 

Similar  comparisons,  illustrating  the  economic  value  due  to 
form  of  apparatus  or  heat  energy  regardless  of  "thermal 
efficiency,"  represented  by  the  "heat  balance,"  may  be  made 
between  steam,  electric  or  gasoline-driven  cars  moving  on  rails 
and  automobile  trucks  or  passenger  automobiles  moving  on 
roads ;  and  internal  combustion  engines  of  two  or  four  cycles  with 
1,  2,  4,  6,  8,  12  or  more  cylinders  to  meet  the  varying  requirements 
of  automobiles,  watercraft,  aircraft,  or  small  isolated  power 
plants. 

While  the  heat  unit  standard  is  a  gauge  of  the  thermal 
value  of  fuel,  it  is  not  a  real  gauge  of  its  economic  value, 
nor  is  the  "  hea(  balance"  a  real  gauge  of  the  economic 
value  of  apparatus. 

Each  form  of  fuel,  electricity  and  appliance  has  its  field  of 
usefulness  as  well  as  its  limitations.  Proper  selection  of  equip- 
meiflt  and  fuel  to  suit  conditions  necessitates  consideration  of  all 
factors  governing  the  accomplishment  of  a  specific  result. 


30 


D-25 
2521 


ECONOMIC     VALUE     OF     BY-PRODUCTS.     POSSIBLE     HEAT     RECOVERY     AND 
THE     EFFECT     OF     OPERATING     CONDITIONS     NOT     CONSIDERED 


BLUE:  WHTER  Gfl5   (COLD  COKE) 

•10%  STEflM 

1.57.  fl5H-rrc. 


BLOW-UP  QflS 

SS.5%  SENSIBLE    HEflT 
BLUE    WflTER   Qfl5 


REVERBERATORS  flIR  FURNflCE 

—  RICHflRDS  — 


.<0e].    WflSTE 
RflDlflTlON-ETC. 


FOUNDRY    CUPOLfl 

—  RICHflRDS  — 


50%  WflSTE  Qfl3-ETC. 


18%    RflDlflTION-ETC. 


HOT  flIR  ENGINE 

—  TRflOC   CflTflLOQ  — 


CONVERSION    L055 


1.5 fo    PUMP  LOSS 


1.57.     IN    WflTER    PUMPED 


OIL  PRODUCER 

—  TEST    RCPOBT  — 


6%    RflDlflTlON  flND 
CONDUCTION 

f.    PILOT  FLflME 
37.    SENSIBLE   MEflT 

15%,   RESlDUflLS 
'-727.    OIL    PRODUCER    Gfl5 


BLflST   FURNflCE 

—  fl.l   &  51.,  MODIFIED - 


5TOVE5 
%    POWER 
25%  SURPLUS  QflS 
•52%   IN  FURNflCE 

10%    EVAPORATION -ETC. 
i 

/  /  /  /  7~A  14%    SLflQ 

%  REDUCTION 
MOLTEN    IRON 


GflSOLENE   flUTOMOBILE: 


13%    FRICTION 
387.  COOLING 

31%   TO  43%  EXhflUST 


-*fl*-  t>7.  TO  107.  flT  ENGINE  SMflTT 


.5  7«  TO  fo%  ROflO  L035 
1.57.  TO   47.     USEFUL    POWER 


Qfl5   ENQINE 

Or   MINES.  MODiriEO- 


35%  EXHFW5T 


PRODUCER  Gfl5    (BITUMINOUS   COflL) 

-w.-5.-M., 


7%     FRICTION   fiND  RflDMTION 


•25%     flT    ENGINE    5MflFT 
31 


157.   SENSIBLE   KflT 
COLD    PRODUCER   Gfl3 


OPEN-HCflRTh  FURNflCE 

-  RICM(WD5, 


7% 

REQENERflTOR   L055 


3% 

21%  CHIMNO 

MOLTEN    3TEEL 


STEflM  LOCOMOTIVE 

—  fl  SM.E  — 


40%  BOILER   LOSS 


201. 

'S////A  wt 

ZZJ  10%  TO  12%  FRICTION 
47.  TO  fe7.    flT    DRflWSflR 

DIESEL   ENGINE 


\£ZZ2  l<«7«    FRICTION  flND  PVMP3 


Factors  Governing  Selection  of  Fuel  or  Electricity 


HE   selection    of   fuel   for    industrial    heating 

should  be  based  upon  appreciation  of  the  radical 
difference  between  the  price  of  fuel,  on  the  one 
hand,  and  the  quality  and  cost  of  product  result- 
ing from  the  generation,  application  and  utilization 
of  heat,  on  the  jother. 

The  result  sought  from  the  application  of  heat  is  pro- 
duced not  by  fuel  or  heat  alone,  but  by  a  combination  of 
equipment,  fuel  and  operative.  These  elements  should  be 
selected  with  regard  to  their  suitability  to  the  conditions  govern- 
ing the  conduct  of  the  operation  as  a  whole,  and  to  their  ability 
to  produce  the  desired  result  at  a  reasonable  cost. 

In  industrial  heating,  as  in  transportation  and  illumination, 
a  complex  field  must  be  surveyed  before  a  proper  selection  of 
fuel  and  equipment  can  be  made.  The  nature  of  the  heating 
process,  the  type  and  size  of  furnaces  adapted  to  the 
manufacturing  requirements,  the  plant  conditions,  the 
personnel,  and  price  of  available  fuels  or  electrical  energy 
are  the  controlling  factors.  Each  of  these  must  be  considered 
together  with  other  essentials  outlined  by  the  chart  on  page  33, 
any  one  of  which  may  influence  the  final  choice. 

The  practice  of  selecting  fuel  on  the  basis  of  thermal 
value  and  price  is  both  inaccurate  and  misleading  unless 
at  the  same  time  proper  consideration  is  given  to  other  essentials 
which  largely  determine  the  suitability  of  fuel  and  equipment 
regardless  of  price  or  thermal  value.  Otherwise,  no  other  form 
of  fuel  could  compete  with  bituminous  coal  burned  in  the  open 
grate  or  blacksmith  fire. 

The  price  of  fuel  may  influence  but  it  certainly  does 
not  determine  the  cost  of  finished  product.  Price  must 
be  considered  with  the  amount  consumed  and  the  suitability 
of  the  "form  value,"  both  of  fuel  and  equipment,  to  the  nature 
of  the  heating  operation  as  a  whole. 

The  form  of  equipment  must  be  considered  with  ref- 
erence to  the  manner  of  applying  and  utilizing  the  heat, 
and  of  handling  the  material  to  be  heat-treated,  because 
these  essentials  are  as  directly  linked  to  the  quality  and  cost 
of  finished  product  as  are  the  price  of  fuel  or  method  of  generating 
heat,  whether  it  be  through  combustion  or  the  arc,  induction 
or  resistance  methods  of  releasing  heat  from  electrical  energy. 

Whenever  there  is  a  difference  in  physical  or  chemical 
form  of  fuel,  or  in  mechanical  form  of  equipment,  there  is 
a  difference  in  economic  value  regardless  of  comparative 
thermal  value  or  price. 

Fuels  of  the  same  physical  form  may  vary  greatly  in 
chemical  composition.  A  difference  in  ash,  sulphur  or 
moisture  content  of  coals,  or  in  percentage  of  inerts,  com- 
bustibles, or  combination  of  the  same  chemical  elements  in 
different  gases,  may  influence  the  choice  regardless  of  price. 
The  difference  between  the  arc,  induction  and  resistance  methods 
of  releasing  heat  may  influence  the  choice  of  equipment  and  the 
form  of  electricity,  i.  e.,  whether  alternating  or  direct  current, 
and  the  voltage,  phase  or  cycle. 

It  is  as  illogical  to  compare  different  forms  of  heat 
energy  with  regard  to  a  certain  result,  as  it  is  to  compare 
electricity  with  any  one  form  of  fuel  on  the  basis  of  thermal 
value,  unless  proper  consideration  is  given  to  the  form 
of  equipment  adapted  to  each. 

In  industrial  heating,  as  in  illumination  or  transporta- 
tion, much  of  the  advantage  frequently  credited  to  some 
one  form  of  energy  is  actually  due  to  the  appliance  em- 
ployed in  connection  with  it.  A  different  design  of  appli- 
ance or  method  of  operating  may  reverse  conclusions  based 
on  thermal  value  or  price. 


The  relative  cost  of  kerosene,  city  gas  or  electricity  on  the 
heat  unit  basis  is  determined  by  the  price  per  gallon,  per  thou- 
sand cubic  feet,  or  per  kilowatt  hour,  respectively,  but  such 
comparisons  do  not  indicate  their  relative  value  as  sources  of 
energy  for  illumination.  The  price  and  form  of  energy  is  usually 
considered  with  the  type  of  lamp,  which  largely  determines  the 
nature  and  cost  of  the  result. 

Frequently  the  "form  value"  of  a  suitable  combination 
of  equipment  and  fuel  will  prevail  regardless  of  price. 

This  is  illustrated  by  the  practice  of  using  comparatively  ex- 
pensive gas  for  intermittent  cooking  operations  in  the  kitchen 
in  preference  to  comparatively  cheap  coal,  which  under  different 
service  requirements  is  preferable  for  heating  the  house.  The 
advantages  of  incandescent  electric  lamps  for  the  illumination 
of  the  interior  of  a  railway  coach  may  be  accompanied  by  the 
use  of  oil  lamps  as  signals  at  the  end  of  the  train. 

Similar  conditions  in  the  field  of  industrial  heating  indi- 
cate the  necessity  of  considering,  in  addition  to  the  apparent 
value  due  to  price  of  fuel,  the  "form  value"  due  to  physical 
condition  or  chemical  composition  of  the  fuel  or  mechanical 
characteristics  of  suitable  equipment,  in  order  to  establish  a 
reasonable  balance  between  the  price  of  fuel  and  the  nature 
and  cost  of  the  heating  operation. 

The  efficient  utilization,  in  suitable  furnaces,  of  the 
right  form  of  fuel  or  electricity,  selected  to  meet  definite 
requirements  of  heating  and  handling,  rather  than  the 
price  alone,  must  be  depended  upon  to  lower  the  cost  and 
improve  the  quality  of  heat-treated  products. 

The  nature  of  the  heating  process,  manufacturing  require- 
ments and  plant  conditions  may  in  many  instances  make  city 
gas  at  $1  per  thousand  cubic  feet  economically  preferable  to  oil 
at  one  cent  per  gallon,  or  coal  at  $1  per  ton.  In  other  instances, 
electricity  at  a  very  much  higher  price,  based  on  equivalent 
energy  cost,  is  given  the  preference  because  of  the  operating 
advantages  made  possible  by  a  specific  form  of  electric  energy 
and  appliance. 

A  fuel  such  as  bituminous  coal  may  be  attractive  on  the 
basis  of  price  but  objectionable  in  form,  or  vice  versa,  as 
in  the  case  of  gas  or  electricity.  Gases  of  the  same  physical 
form  may  vary  greatly  in  chemical  composition,  which  in  itself 
may  limit  the  field  of  usefulness  regardless  of  price.  Suitable 
furnace  design  may  overcome  these  objections.  Thus  the 
use  of  bituminous  coal  is  made  possible  in  enameling  furnaces 
by  the  use  of  a  muffle,  which  might  be  unnecessary  in  electric 
furnaces  in  which  gases,  if  any,  originating  from  the  resistance 
material  did  not  affect  the  product  to  be  heated. 

The  innumerable  factors  controlling  the  selection  of  fuel 
and  the  generation,  application  and  utilization  of  heat  for 
industrial  or  domestic  purposes,  denotes  a  field  of  useful- 
ness, in  suitable  apparatus,  for  all  varieties  of  solid, 
liquid,  gaseous  and  electrical  fuel  or  heat  energy. 

Extension  of  the  use  of  any  one  form  of  fuel  or  electricity 
automatically  follows  the  development  of  apparatus  for  con- 
verting that  form  of  energy  into  useful  service  in  heat,  power 
or  illumination.  The  apparent  relative  economic  value  of  the 
different  forms  on  the  basis  of  price,  at  the  moment,  may  be 
changed  in  the  future,  as  it  has  been  in  the  past,  by  the  develop- 
ment of  better  methods  of  heat  application  and  more 
efficient  apparatus  to  make  possible  either  a  different 
result  or  to  accomplish  the  same  result  at  less  cost,  by 
decreasing  the  amount  of  energy  required  without  any  change 
in  the  price. 


32 


Itf«  IS    I  s      v  § 


u  -<         ow  T>          »      * 

LJ  I     3       B      tJ  LJ       5    1 

V J         I I 1 1 ,1 L 


L  5                                                        ; 

0 

1 

i_i    i     »a  ssg ' 
p=^ —    52  i  i  i : 


; 


33 


Comparative  Prices  of  Fuel  on  B.  T.  U.  Basis 


HE  chart  on  page  35  affords  a  ready  means  of 
comparing  fuels  on  the  basis  of  their  B.  t.  u. 
cost — by  direct  comparison  of  the  price  of  one 
fuel  with  the  price  of  another;  by  comparison 
of  the  relative  qosts  per  million  B.  t.  u.,  or,  on 

an   assumed   cost   per    million   B.   t.   u.,    reading   directly  the 

"permissible"  prices  for  various  fuels. 

The  horizontal  lines  represent  prices  for  fuels;  the 
vertical  lines,  costs  per  million  B.  t.  u.  of  heat  energy;  the 
diagonal  lines  are  the  plotted  heat  unit  values  of  fuels. 

The  chart  is  read  by  converting  the  price  of  a  given  fuel  (hori- 
zontal line),  at  its  intersection  with  the  diagonal  line  of  the  heat 
unit  value  of  the  fuel  in  question,  to  the  vertical  intersecting 
line  which,  read  at  the  bottom  of  the  chart,  indicates  the  cost 
per  million  B.  t.  u.,  or  vice  versa. 

To  illustrate:  For  a  comparison  of  12,000  B.  t.  u.  coal  at 
$5.00  per  ton  with  fuel  oil.  Reading  from  the  left  scale,  the 
horizontal  line  from  $5.00  per  ton  is  followed  to  its  intersection 
with  the  diagonal  value  line  for  12,000  B.  t.  u.  coal,  then  verti- 
cally down  to  the  scale  at  the  bottom  of  the  chart,  which  in- 
dicates a  cost  of  approximately  21c  per  million  B.  t.  u.  The 
same  vertical  line  is  followed  to  its  intersection  with  the  diagonal 
value  line  for  fuel  oil,  then  horizontally  to  the  scale  on  the  right 
of  the  chart,  which  indicates  a  price  of  approximately  3c  per 
gallon,  at  which  such  fuel  oil  would  have  to  be  procured  to 
equal  on  a  heat  unit  cost  basis  12,000  B.  t.  u.  coal  at  $5.00  per 
ton. 

Reversing  this  process,  if  fuel  oil  should  cost  8c  per  gallon, 
this  horizontal  line  carried  to  its  intersection  with  the  fuel  oil 
diagonal,  then  down  to  the  bottom,  indicates  a  cost  of  approxi- 
mately 56c  per  million  B.  t.  u.  This  same  vertical  line  carried 
to  its  intersection  with  the  12,000  B.  t.  u.  coal  diagonal,  then 
horizontally  to  the  left,  indicates  a  comparative  price  for  coal 
of  $13.50  per  ton.  Direct  comparisons  are  thus  available  be- 
tween the  coal  and  fuel  oil  prices;  indicating  that  fuel  oil  would 
have  to  be  available  at  3c  per  gallon  to  equal  in  heat  unit  cost 
12,000  B.  t.  u.  coal  at  $5.00  per  ton;  and  that  if  fuel  oil  cost  8c 
per  gallon,  12,000  B.  t.  u.  coal  would  be  no  higher  in  B.  t.  u.  cost 
at  $13.50  per  ton. 

This  method  of  comparison  takes  into  account  the  cost 
per  million  B.  t.  u.  merely  as  an  intermediate  step.  If 

desired,  fuel  prices  may  be  compared  directly.  For  example, 
following  along  the  horizontal  line  of  $5.00  per  ton  coal  to  its 
intersection  with  the  diagonal  12,000  B.  t.  u.  coal  value  line, 
then  vertically  down  to  the  intersecting  diagonal  line  for  fuel 
oil,  then  horizontally  to  the  right,  reading  directly  the  com- 
parative price  of  3c  per  gallon  for  fuel  oil. 

At  an  assumed  cost  per  million  B.  t.  u.,  the  "permissible" 
prices  for  the  various  fuels  to  be  considered  will  be  found  by 
following  the  vertical  "cost  per  million  B.  t.  u. "  line  to  its 
intersection  with  each  of  the  fuels  in  question,  then  to  the  right 
or  left  respectively  to  read  the  "cents  per  gallon"  for  a  liquid 
fuel,  the  "dollars  per  ton"  for  a  solid  fuel,  or  the  "cents  per 
thousand  cubic  feet"  for  a  gaseous  fuel. 

In  the  cases  of  acetylene  gas  and  electricity,  the  prices 
are  read  to  the  left  and  right  respectively  of  the  chart  as 
cents  per  hundred  cubic  feet  and  per  Kw.h.  The  ver- 
tical intersecting  lines,  however,  must  be  read  at  the 
extreme  bottom  of  the  chart  as  dollars  per  million  B.  t.  u. 
and  transposed  accordingly  for  comparison  with  the  other  fuels 
which  are  rated  at  cents  per  million  B.  t.  u. 


The  chart  "Industrial  Fuels"  on  page  44  furnishes  a  direct 
B.  t.  u.  cost  comparison  of  the  ordinary  industrial  fuels  based 
on  assumed  prices  which  approximate  the  present-day  market. 

These  charts  have  been  prepared  to  facilitate  a  comparison 
of  the  B.  t.  u.  cost  of  fuels,  but  in  making  such  comparisons  it 
must  always  be  borne  in  mind  that  B.  t.  u.  costs  are  but  one 
factor,  and  in  most  cases  the  minor  factor,  affecting  the  total 
cost  of  any  heating  operation  or  the  manufacture  of  any  heat- 
treated  product. 

If  mass  generation  of  heat  is  considered  without  refer- 
ence to  its  nature  or  use,  then  the  B.  t.  u.  cost  of  fuel 
would  be  the  factor  determining  the  choice.  In  prac- 
tically all  cases,  however,  the  combustion  of  fuel — the  generation 
of. heat — is  a  preliminary  to  the  application  and  utilization  of 
heat  in  the  accomplishment  of  a  required  result,  and  in  every 
instance  there  must  first  be  considered  the  suitability  of  a 
fuel  to  the  nature  of  the  operation,  equipment,  and  the 
general  operating  conditions. 

Much  the  same  situation  exists  as  in  the  case  of  foods, 

which  are  frequently  considered  as  a  form  of  fuel.  Certain 
foods  may  be  low  priced  in  relation  to  their  potential  value  in 
calories,  and  yet  not  suitable  for  use  under  every  condition. 
Baked  beans,  for  example,  represent  a  low-priced  food,  and  yet 
for  the  convalescent  requiring  a  large  amount  of  nourishment, 
such  relatively  high  cost  foods  of  different  character  as  milk, 
eggs,  animal  jellies,  etc.,  may  be  given  the  preference.  The 
choice  should  be  based  not  alone  on  the  relative  value  in  calories 
of  such  foods,  but  with  regard  to  their  suitability  to  the  indi- 
vidual requirements. 

The  term  "form  value"  is  suggested  to  give  expression  to  the 
intangible  value  due  to  difference  in  physical  characteristics  and 
chemical  association  that  exists  between  the  various  fuels; 
and  it  is  the  "form  value"  —  in  addition  to  price — of  a  fuel, 
influenced,  of  course,  by  the  design  and  method  of  operating 
the  equipment  employed  with  it,  that  largely  determines  its 
economic  value  and  field  of  usefulness. 

It  is  the  advantages  due  to  "form  value"  of  electricity 
with  suitable  appliances  which,  under  certain  conditions, 
suggests  its  use  for  illumination  when  gas  or  oil  might 
be  cheaper  on  a  B.  t.  u.  basis.  Similar  conditions  may 
suggest  the  use  of  gas  with  the  modern  gas  range  for  cooking 
in  preference  to  coal,  wood  or  oil  at  a  lower  B.  t.  u.  price.  Dif- 
ferent conditions  may  warrant  the  choice  of  lower-priced  fuels 
which,  with  suitable  apparatus,  may  meet  the  operating  require- 
ments at  reasonable  cost. 

With  fuel,  as  with  food,  the  choice  is  determined  not  by 
the  relative  heat  unit  cost,  but  by  consideration  of  price 
with  "form  value"  of  the  fuel  and  equipment  adapted 
to  it,  and  the  suitability  of  the  combination  to  definite 
operating  conditions. 

A  comparison  of  fuels  on  the  basis  of  B.  t.  u.  value  is  not 
a  test  of  economic  value  unless  the  fuels,  so  compared 
have  the  same  physical  characteristics  and  chemical 
association  and  are  utilized  in  appliances  having  the  same 
mechanical  characteristics  and  operated  under  the  same 
conditions. 

Price  of  fuel  is  but  one  item  in  the  cost  of  heating, 
just  as  it  is  but  one  item  in  the  cost  of  transportation  or 
illumination.  Operating  cost  includes  not  only  the  price  of 
fuel,  but  also  the  quantity  consumed,  which  is  largely  governed 
by  the  manner  of  applying  and  utilizing  the  heat  in  useful 
service.  This  in  turn  is  greatly  influenced  by  the  design  and 
method  of  operating  the  appliance,  whether  it  be  a  furnace  or 
a  motor  truck. 


34 


CENTS  PER  GALLON  OF  LIQUID  FUEL  OR  PER  kw.ll.  OF  ELECTRICITY, 

oo    r--    co  ira  «o-    co  cxi   *—    c 


DOLLARS  PER  TON  (2000  Ib.)  OF  SOLID  FUEL, 


00 


_gggsg°ss 

CENTS  PER  1000  cu.ll.  OF  GASEOUS  FUELS  OR  PER  100  Ctl.ft,  OF  ACETYLENE  GAS, 


35 


Comparative  Heating  Value  of  Industrial  Fuel  Gases 


HE  relative  value  of  gases  for  industrial  or 
domestic  heating  or  power  service  is  not  defi- 
nitely determined  by  the  customary  method 
of  comparison  on  the  basis  of  heat  units  (B. 
t.  u.)  per  cubic  foot. 

It  is  a  common  belief  that  the  suitability  of 
a  gas  as  a  source  of  heat  or  power  is  determined  by  its  B.  t.  u. 
value  and  price,  and  that  gases  higher  in  B.  t.  u.  per  cubic  foot 
are  the  more  desirable;  but  this  is  far  from  true. 

The  heat  unit  content  of  a  gas  is  not  a  true  indication 
of  its  heating  value  in  an  economic  sense.  In  addition  to 
the  B.  t.  u.  value  there  must  be  considered  the  chemical  com- 
position of  the  gas  and  of  the  mixture  of  gas  and  air  supplied 
for  combustion,  and  also  the  influence  of  the  design  of  furnace 
or  other  appliance  employed  for  the  generation,  application 
and  utilization  of  the  heat. 

The  chemical  composition  of  a  gas  fixes  the  volume  of 
air  required  for  combustion,  and  the  mixture  so  formed, 
from  which  the  heat  is  released,  has  a  B.  t.  u.  value  per 
unit  of  volume  much  less  than  that  of  the  original  gas 
itself.  The  quantity  of  air  required  for  combustion  of  the 
various  gases  fluctuates  greatly,  being  more  for  the  richer  gases 
and  in  general  less  with  the  decrease  in  B.  t.  u.  value. 

The  heat  unit  value  of  the  usual  industrial  gases  may  vary 
from  100  to  1500  B.  t.  u.  per  cubic  foot;  the  theoretical  quantity 
of  air  required  for  combustion  may  vary  from  one  to  twelve 
cubic  feet  per  cubic  foot  of  gas;  the  B.  t.  u.  value  of  the  com- 
bustible mixtures  of  these  same  gases,  with  the  theoretical 
quantity  of  air  required  for  combustion,  may  vary  from  50  to 
115  B.  t.  u.  per  cubic  foot,  or  less  with  an  increase  in  the  relative 
quantity  of  air  supplied.  See  chart  page  37. 

The  B.  t.  u.  value  of  a  gas  or  its  combustible  mixture 
does  not  indicate  the  temperature  obtainable  by  com- 
bustion or  determine  its  field  of  usefulness. 

Natural  gas  at  900  B.  t.  u.,  while  apparently  three  times 
as  rich  as  water  gas  at  300  B.  t.  u.  per  cubic  foot,  has  a  lower 
flame  temperature  and  rate  of  flame  propagation.  Natural  gas 
would  not  be  as  suitable  as  water  gas  for  high  temperature 
blow-pipe  operations,  such  as  welding.  On  the  other  hand, 
natural  gas  is  preferable  to  water  gas  in  internal  combustion 
engines,  in  which  the  air  and  gas  are  mixed  under  heavy  com- 
pression. 

Producer  gas,  in  its  washed  state,  while  suitable  for  gas 
engines,  is  not  as  well  suited  as  water  gas  for  high  temperature 
operations,  such  as  forging  or  welding,  yet  with  regenerative 
furnaces  it  is  extensively  used  for  melting  steel.  The  design 
and  operation  of  the  furnace  favor  a  field  of  usefulness 
which  is  not  disclosed  by  an  analysis  of  the  gas  itself. 

Both  these  gases  and  the  air  required  for  their  combustion 
may  be  preheated  to  a  high  temperature  in  regenerative  fur- 
naces. If  natural  gas  were  employed  in  the  same  furnaces, 
the  preheating  would  be  limited  to  the  air  alone,  because  the 
natural  gas,  by  reason  of  its  chemical  composition,  would  dis- 
sociate in  the  regenerative  chambers  at  high  temperatures. 

Many  examples  from  every-day  practice  with  various  forms 
of  fuel  could  be  given  to  illustrate  the  point  not  generally  ap- 
preciated, that  the  difference  in  composition  or  "chemical 
form  value"  of  industrial  gases,  the  influence  of  the 
quantity  of  air  supplied  for  combustion,  and  the  design 
of  the  appliance,  denote  fields  of  usefulness  and  limitations 
which  are  not  revealed  by  the  customary  B.  t.  u.  com- 
parison. 

The  distribution  of  natural  gas  is  frequently  affected  in  cold 
weather  by  the  formation  of  solids  in  the  pipe  lines.  The  dis- 


tribution of  carbureted  water  gas  under  similar  conditions 
frequently  results  in  the  deposition  of  oil  in  the  pipe  lines  re- 
sulting from  condensation  of  certain  hydrocarbons  peculiar  to 
this  gas.  Producer  gas,  while  relatively  cheap  and  less  susceptible 
to  such  conditions  in  transportation,  is  not  suitable  for  general 
distribution  by  reason  of  its  low  heating  value  and  unusually 
high  percentage  of  incombustibles. 

By  reason  of  their  composition,  gases  such  as  acetylene  or 
blue  water  gas  have  a  more  or  less  well  denned  field  of  usefulness, 
which  makes  them  unsuited  for  the  average  domestic  or  industrial 
heating  requirements. 

"City  gas"  is  well  adapted  to  the  average  industrial  and 
domestic  heating  operations.  As  a  domestic  fuel  it  has  become 
almost  indispensable,  particularly  in  congested  districts.  An 
efficient  extension  of  its  use  is  highly  desirable  for  the  influence 
it  will  exert  on  conditions  of  living  and  manufacturing  and  in 
conservation  of  fuel  resources.  Its  field  of  usefulness  in  industrial 
heating,  at  present,  is  narrowed  by  relatively  high  price  and 
comparatively  inefficient  appliances. 

The  prevailing  high  price  of  "city  gas"  is  very  largely 
due  to  existing  costly  and  wasteful  methods  employed 
in  its  manufacture  and  distribution — an  inheritance  from 
the  days  when  gas  was  used  primarily  for  illumination.  This 
results  either  in  a  needless  production  of  "domestic  coke" 
or  the  use  of  oil  and  anthracite  coal,  which  could  be  well 
diverted  to  more  essential  purposes. 

The  improvement  of  electric  appliances,  resulting  in  an 
extension  of  the  use  of  electricity  for  many  industrial  heating 
operations  which  could  be  efficiently  conducted  with  gas,  is 
gradually  developing  an  appreciation  of  the  fact  that  the  cus- 
tomary methods  of  gas  manufacture  and  utilization  must 
be  superseded  by  others  better  adapted  to  present-day 
conditions  if  the  gas  industry  is  to  survive  and  render 
its  full  measure  of  service. 

The  need  may  be  supplied  by  a  "fuel  gas"  generated  through 
complete  gasification  of  bituminous  coal,  under  standards  which 
will  eliminate  the  oil  or  anthracite  coal  or  "domestic 
coke"  to  maintain  obsolete  candle-power  requirements 
or  unnecessarily  high  heat-unit  value.  The  heating  value 
could  be  lowered  to  approximately  400  B.  t.  u.,  which,  with 
suitable  chemical  composition  to  meet  requirements  of  flame 
temperature  and  odor,  would  be  well  suited  to  present-day 
domestic  and  industrial  conditions;  for,  as  indicated  by  the 
chart  on  page  37,  it  would  be  substantially  equal  to  the  present- 
day  "city  gas"  in  heating  value. 

Low-priced  gas  of  the  proper  heat  value  and  chemical 
composition  is  not  in  itself  sufficient,  because  the  cost  and 
nature  of  service  to  the  consumer  are  determined  not  by 
price  alone,  but  by  the  quantity  consumed  and  the  design 
of  heating  appliances.  The  appalling  waste  of  natural  gas 
in  the  operation  of  industrial  furnaces,  which  generally  lack 
the  essentials  of  air  control  and  dampers  provided  with  the 
common  coal  kitchen  range  or  house  heater,  and  the  influence 
of  excess  air  in  lowering  the  heating  value  of  gases,  indicate 
the  influence  of  furnace  design  and  operation  upon  the 
quality  and  cost  of  the  heating  service. 

Electricity,  at  a  much  higher  price  on  equivalent  energy 
basis,  has  outdistanced  gas  for  many  industrial  heating 
operations;  not  always  by  reason  of  inherent  advantage  in 
electricity  itself,  but  by  reason  of  its  use  in  more  efficient 
furnaces  or  other  appliances.  A  comparison  of  the  relative 
thermal  efficiency  of  the  average  gas  appliance  with  electrical 
appliances  offered  for  the  same  purpose,  indicates  the  need  for 
improvement  and  the  influence  of  the  design  and  operation 
of  equipment  upon  the  cost  of  product  or  heating  service, 
of  which  the  price  of  fuel  is  but  one  factor. 


36 


COMPARISON    OF    INDUSTRIAL    GASES 

APPROXIMATE     COMPOSITION— ENERGY     CONTENT     AND     CALORIFIC     INTENSITY 

OF 

GASES     AND     COMBUSTIBLE     MIXTURES 

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Composition  of  Industrial  Fuel  Gases 


HE  composition  of  industrial  gases,  their  com- 
bustible mixtures,  and  products  of  combustion, 
are  essential  factors  governing  the  selection  of 
gases  and  suitable  equipment  for  the  production 
and  application  of  heat,  power  or  light. 

When  a  gas  is  to  be  used  as  a  reducing  agent  or  for 
some  special  purpose  not  requiring  combustion,  the  composition 
of  the  gas  itself  is  generally  all  that  need  be  considered.  When 
employed  as  a  source  of  heat  energy,  however,  it  is  necessary 
to  consider  many  other  factors  outlined  by  the  chart  on  page 
33,  with  particular  reference  to  the  influence  of  the  composi- 
tion of  the  gas  or  its  combustible  mixture  upon  the 
nature  of  the  operation  to  be  conducted  and  the  design  of 
apparatus  to  be  employed  for  the  generation  and  application 
of  heat. 

When  the  material  difference  in  B.  t.  u.  value  of  the  common 
industrial  gases  is  considered  together  with  the  comparatively 
slight  difference  in  heating  value  of  their  combustible  mixtures, 
it  is  apparent  that  chemical  composition  is  of  greater  im- 
portance than  B.  t.  u.  value  in  determining  their  field  of 
usefulness. 

The  quantity  of  inerts  or  incombustibles  is  relatively 
small  in  the  majority  of  industrial  gases,  with  the  exception 
of  producer  gas,  of  which  over  60%  is  inert  matter.  The  inert 
content  is  important  insofar  as  it  relates  to  the  increase  in 
volume  of  gas  or  combustible  mixture  necessary  to  furnish  a 
given  amount  of  heat  energy,  and  to  the  nature  and  cost  of 
equipment  and  operations  necessary  for  manufacture  and  dis- 
tribution; but  it  is  apparent  from  comparison  of  the  inert 
content  of  the  combustible  mixtures  of  the  different  gases  that 
the  heating  value  of  the  gases  is  determined  more  by  the 
elements  forming  the  combustibles  than  by  the  per- 
centage of  inerts  in  the  gases  or  in  their  combustible 
mixtures. 

In  the  generation  and  utilization  of  heat,  we  are  con- 
cerned more  with  the  heating  value  and  composition  of 
the  combustible  mixture  than  with  that  of  the  gas  itself, 

although  the  composition  of  the  gas  enters  into  the  problem 
of  distribution,  as  is  illustrated  by  the  action  of  carbureted 
water  gas,  oil  gas  and  natural  gas  in  cold  weather. 

The  relative  importance  of  chemical  composition,  with 
reference  to  both  the  character  of  the  heat  released  and  the 
chemical  influence  of  the  products  of  combustion  upon  the 
product  to  be  heated  or  heating  apparatus,  is  not  generally 
appreciated.  The  striking  changes  resulting  from  the 
mixture  of  gas  and  the  air  necessary  for  combustion, 
the  further  changes  following  ignition  and  combustion, 
and  the  influence  of  excess  air,  are  illustrated  by  the  chart 
on  page  39. 

Consideration  of  the  comparatively  large  volume  of  products 
of  combustion  of  each  gas,  which  are  heated  to  the  maximum 
temperature  of  the  heating  process,  will  indicate  the  economies 
attainable  through  efficient  utilization  of  the  spent  gases 
to  perform  useful  work.  The  heat  in  these  gases  may  be  utilized 
to  preheat  the  air  or  fuel  prior  to  combustion,  or,  as  is  generally 
more  desirable,  to  preheat  the  material  before  it  is  exposed  to 
the  final  working  temperature. 

The  spent  gases  may  be  considered  as  a  vehicle  for 
conveying  heat  in  the  manner  that  a  wire  is  employed  in  con- 
veying electricity.  So-called  quiescent  atmospheres  do 
not  actually  exist.  The  advantages  that  result  from  the 
transfer  of  heat  by  convection,  and  the  natural  motion  of  hot 
gases  created  by  a  temperature  differential,  regardless  of  the 
source  or  manner  of  heat  generation,  indicate  the  possibility 
of  utilizing  an  apparent  disadvantage  in  composition  not  only 
for  effecting  economy  in  fuel  but  for  improvement  in  methods 
of  heat  application. 

The   efficiency   of   such    utilization    is   dependent   upon 


the  design  of  the  furnace  or  other  appliance,  and  particularly 
the  method  of  heat  application  and  manner  of  handling  the 
material  and  exposing  it  to  the  heat. 

The  field  of  usefulness  of  any  gas  is  not  entirely  de- 
pendent upon  the  B.  t.  u.  value  or  composition  of  the 
combustible  mixture  or  products  of  combustion.  The 

design  of  equipment  and  method  of  releasing  heat  exert  no 
small  influence  upon  the  operating  result,  and  necessitate  con- 
sideration of  the  physical  conditions  governing  the  design  of 
mixers,  combustion  chambers,  rate  of  energy  input,  temperature, 
time  and  other  factors  which  are  not  apparent  in  the  gas  itself. 

The  comparatively  high  calorific  intensity  of  water  gas  makes 
it  unsuited  to  certain  forms  of  equipment,  such  as  gas  engines, 
which  may  be  employed  to  advantage  with  others,  such  as 
natural  gas,  city  gas  or  producer  gas.  This  relation  may  be 
reversed  in  other  operations  requiring  the  use  of  blow  torches 
or  special  heating  equipment  for  high  temperature  operations. 

The  composition  of  the  products  of  combustion  must 
be  considered  in  relation  to  its  influence  upon  the  product, 

because  furnace  atmosphere  plays  an  important  part  in  some 
processes  which  may  require  either  reducing,  neutral  or  oxidiz- 
ing conditions. 

The  apparent  advantages  of  a  comparatively  cheap 
fuel  may  be  offset  by  the  chemical  action  of  the  resultant 
gases  upon  the  process  or  apparatus,  which  would  necessitate 
modifications  in  the  furnace  design  or  process  in  order  to  retain 
the  advantage  that  may  be  represented  by  the  form  or  price 
of  such  fuel.  This  is  illustrated  by  the  practice  of  employing 
crucibles  for  melting  certain  metals  to  decrease  the  possible 
effect  of  oxidation,  of  packing  material  in  sealed  boxes  or  pots, 
and  by  the  muffle  type  of  furnace  employed  for  vitreous  enamel- 
ing; in  each  case  permitting  the  application  of  heat  without 
contact  between  the  material  to  be  heated  and  the  products  of 
combustion.  Special  atmospheres  may  be  secured  in  muffles 
by  passing  suitable  gases  into  the  muffle,  which  may  or  may 
not  be  sealed. 

Such  limitation  is  not  confined  to  fuels  alone,  as  it  is 

frequently  encountered  in  the  arc  or  resistance  methods  of 
releasing  heat  from  electricity  due  to  the  gasification  of  the 
electrodes  or  resistance  material.  In  most  cases  it  is  desirable 
to  maintain  neutral  or  reducing  atmosphere  in  the  heating 
zone  to  protect  the  material  from  oxidation.  While  this  may  be 
readily  accomplished  with  most  fuels  in  properly  designed 
furnaces  by  control  of  the  air  supplied  for  combustion,  it  is 
comparatively  difficult  with  others.  Such  a  neutral  or  reducing 
atmosphere  may  be  readily  secured  in  electric  furnaces  releasing 
heat  through  some  form  of  carbonaceous  resistance  material, 
while  a  different  form  of  resistance  material  may  necessitate  the 
use  of  a  material  such  as  oil  to  provide  the  proper  atmosphere 
in  the  heating  zone,  even  though  the  heat  itself  is  generated  by 
an  electrical  process. 

The  gases,  such  as  coal  gas,  carbureted  water  gas,  etc., 
commonly  known  as  "city  gas"  of  about  600  B.  t.  u.,  have 
a  lower  flame  temperature  than  unmixed  blue  water  gas  of 
about  300  B.  t.  u.,  although  the  B.  t.  u.  values  of  the  combustible 
mixtures  are  approximately  the  same.  The  difference  in  chemical 
composition  of  the  gases  themselves,  resulting  in  a  compara- 
tively insignificant  difference  in  odor,  which  is  frequently  desir- 
able in  order  to  detect  leaks,  makes  the  so-called  "city  gas" 
generally  preferable  for  distribution  to  domestic  consumers. 
Likewise,  the  difference  in  chemical  composition  of  the 
combustible  mixture  or  the  products  of  combustion 
frequently  determines  the  field  of  usefulness  in  heat, 
power  or  illumination,  regardless  of  price  on  a  heat-unit 
basis. 

The  fundamental  significance  of  chemical  composition, 
as  affecting  the  quality  and  cost  of  product,  must  be  con- 
sidered in  the  selection  of  gases  and  of  equipment  for 
the  transformation  and  application  of  their  energy  values. 


38 


D-21 
292O 


COMPARISON    OF    INDUSTRIAL    GASES 

VOLUMETRIC     COMPOSITION 

OF 
GAS.    COMBUSTIBLE     MIXTURE     AND     PRODUCTS     OF     COMBUSTION 


CRR6URETTED    WflTER    Qfl5 
I  I  I 


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CwHM-  ILUUMINflNTS 
cO-CflRBON   MONOXIDE 
Qz-  OA^QEN 
COs-CflRBON   CXOWOC 
HaO-  WfTTER 


I        i 


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OF  QflS. 

B=  COMBUSTIBLE    MIXTURE 
THEORETlCflL   RIR    SUPPLY 

C  =  PRODUCTS  OF  COMBUSTION 
THEORETICAL  fill?    5UPPLV. 

D=  COMBUSTIBLE    NllXTUf?E 
100^   EXCESS   flll? 
E'PPCODUCTS   OF  COMBUSTION 
EXCE35    fllf? 


39 


Fig. 


Utilization  of  Fuel  Resources 


HE  so-called  "fuel  problem"  is  but  one  factor 
in  the  real  problem,  i.  e.,  the  efficient  utilization 
of  all  the  energy  and  commodity  values  in  natural 
fuel  resources. 

As  regards  the  energy  values  alone,  the  problem 
involves  the  production,  transportation  and  utiliza- 
tion of  fuel  in  the  application  of  heat,  power  or  light. 

A  field  of  usefulness  exists  for  each  form  of  fuel  used 
in  suitable  apparatus.  The  scope  of  the  respective  fields  is 
not  measured  solely  by  price  and  thermal  value,  but  includes 
that  intangible  value  due  to  the  physical  or  chemical  association 
of  the  fuels  and  the  mechanical  form  of  the  apparatus.  This 
element  may  be  defined  as  "form  value,"  in  contrast  to  thermal 
value  as  commonly  expressed  in  "heat  units"  (B.  t.  u.)  or  "heat 
balance. "  A  survey  of  the  field  •  is  incomplete  without 
consideration  of  all  the  factors  that  govern  the  produc- 
tion and  transportation  of  fuel,  and  the  selection  of  the 
proper  form  of  fuel  and  proper  equipment  for  the  efficient 
application  of  heat  to  useful  work. 

"A  solution  of  the  fuel  problem"  is  frequently  advanced 
by  advocates  of  some  one  form  of  fuel,  or  those  urging  the 
proposition  that  the  utilization  of  fuel  for  the  generation  of 
electricity,  or  production  of  gas  in  super-transforming  stations, 
is  the  logical  method  of .  conserving  fuel  resources  in  meeting 
the  modern  demand  for  energy  service. 

However,  the  requirements  for  power,  illumination,  industrial 
and  domestic  heating,  and  the  chemically  important  need  for 
by-products  are  so  interwoven  that  all  these  needs  cannot  be 
separately  treated.  The  energy  and  commodity  require- 
ments must  be  appraised  in  their  interdependence,  and 
determination  made  of  the  most  practical  means  for 
meeting  these  requirements.  Economies  that  may  be 
effected  in  production  and  transportation  of  fuel  must  be  con- 
sidered together  with  the  possible  economies  in  utilization  of 
different  forms  of  solid,  liquid  and  gaseous  fuels  and  electrical 
energy  in  more  efficient  appliances  adapted  to  each. 

The  possibility  of  improving  present  methods  must  be 
borne  in  mind,  as  well  as  the  advantages  likely  to  result  from 
the  substitution  of  better  methods  adapted  to  present-day 
conditions.  The  quantity  of  fuel  required  to  meet  the  country- 
wide demand  has  grown  to  such  a  stupendous  total  that  its 
provision  in  the  customary  forms  is  becoming  increasingly 
difficult  and  results  in  tremendous  wastes  of  material  and  effort. 

The  waste  in  production  of  oil  is  far  greater  in  proportion 
than  that  of  coal,  but  the  waste  in  transportation  and 
utilization  is  proportionately  greater  with  coal.  The  handling 
of  coal  engages  over  one-third  the  freight  capacity  of  the 
country,  while  the  more  flexible  form  of  oil  favors  its  simple 
and  cheap  distribution  through  an  extensive  system  of  pipe 
lines  thousands  of  miles  in  length.  Conversion  of.  the  heat 
energy  in  coal  to  the  form  of  gas  simplifies  the  problem 
of  distribution  and  utilization,  particularly  in  congested 
areas,  which  condition  warrants  consideration  of  "form  value" 
in  distribution  as  well  as  in  utilization. 

The  traffic  congestion  at  the  terminals  and  on  the  streets, 
from  the  distribution  of  coal  and  removal  of  ash,  and  the  enor- 
mous losses  and  property  damage  due  to  smoke,  soot  and  ash, 
as  also  the  loss  by  destruction  of  valuable  by-products,  etc., 
following  the  transportation  and  use  of  coal  in  the  customary 
manner  and  form,  are  in  marked  contrast  to  the  conditions 
made  possible  by  substitution  of  the  more  mobile  forms  of  energy 
such  as  oil,  gas  or  electricity.  These  contrasting  conditions 


illustrate  the  influence  of  the  "form  value"  of  energy  and 
appliances  upon  the  cost  of  transportation  and  ultimate 
cost  at  the  point  of  consumption. 

In  1915,  before  the  price  of  coal  was  advanced  by  war  con- 
ditions, the  average  cost  of  bituminous  coal  at  the  mines  was 
less  than  $1.25  per  ton.  The  difference  between  this  figure 
and  the  price  paid  by  the  consumer  represented  the  charges  of 
the  carriers  and  dealers,  from  which  it  is  apparent  that  any 
economies  possible  through  improved  methods  of  pro- 
duction would  have  exerted  very  little,  if  any,  influence 
in  reducing  the  price  to  the  consumer. 

As  an  illustration  of  what  can  be  gained  by  transforming 
its  energy  into  other  forms,  in  addition  to  the  saving  in  trans- 
portation: The  same  coal  utilized  in  the  by-product  coke  oven, 
or  the  central  station  gas  plant  by  the  coal-gas  process,  has 
been  made  to  yield  domestic  coke,  gas  for  heating  and  illumina- 
tion, and  by-products  valued  at  about  $15.  If  its  energy  values 
were  entirely  converted  into  a  gas  suitable  for  the  average 
domestic  and  industrial  heating  requirements  or  for  the  genera- 
tion of  power,  the  yield  in  gas  and  by-products  would  be  over 
$25.  Additional  gains  resulting  from  the  transportation 
of  energy  in  the  form  of  gas  through  pipes,  or  electricity 
by  wires,  are  obvious,  including  the  diversion  of  coal-carrying 
equipment  to  more  essential  and  profitable  uses;  the  saving  in 
fuel  incident  to  better  methods  of  heat  application  possible 
with  gas  or  electricity,  and  a  general  improvement  in  living 
conditions. 

The  losses  and  likewise  the  opportunities  for  improve- 
ment in  the  utilization  of  fuel  are  shown  by  the  diagrams 
on  page  41,  representative  of  current  practice.  When  the 
additional  losses  in  the  production  and  transportation  of 
fuel  before  its  combustion  are  considered  together  with  the 
still  greater  losses  in  the  application  of  heat,  power  or 
light  after  transformation,  the  condition  is  still  more  striking 
and  suggests  the  desirability  of  improvement  in  methods  of 
utilizing  the  energy  resources. 

An  extension  of   the  electrical   program   is  desirable  to 

meet  the  need  for  power  and  illumination,  but  the  limitations  of 
price  and  "form  value"  in  the  arc,  resistance  and  induction 
methods  of  releasing  heat,  and  the  special  nature  of  electrical 
equipment,  limit  the  field  of  electricity  as  a  substitute  for  fuel 
in  heating  operations. 

Reconstruction  of  the  "city  gas"  industry  offers  an  at- 
tractive field  for  development  because  of  the  opportunity  for 
better  utilization  of  the  heat  energy  in  bituminous  coal  and  the 
economic  progress  that  will  follow  an  extended  use  of  cheaper 
gas.  Better  methods  of  gasification  and  distribution, 
elimination  of  the  problems  incident  to  the  use  of  oil, 
anthracite  coal  and  "domestic  coke,"  and  utilization  in 
improved  appliances,  such  as  furnaces,  gas  engines,  etc., 
should  result  in  better  and  cheaper  methods  of  utilizing 
fuel  resources,  with  advantage  to  the  community  as  well  as 
the  gas  industry. 

That  one  coal  pile  and  transforming  station  may  be  a 
source  of  by-products  and  energy  in  the  form  of  gas  or 
electricity  for  domestic  and  industrial  heating  is  not  an 
idle  dream.  Every  essential  step  has  been  proved  in  practice. 
Public  opinion  needs  to  be  awakened  to  the  advantages  that 
will  follow  further  extended  use  of  the  more  mobile  forms 
of  heat  energy,  such  as  gas  or  electricity,  and  to  the  fact 
that  those  advantages  can  be  gained,  however,  only  through 
far-reaching  changes  in  present  methods  of  provision  and 
utilization. 


40 


HEAT   DISTRIBUTION    IN    ENERGY   CONVERSION   PROCESSES 

ECONOM.C     VALUE     OF     BY-PRODUCTS.     POSSIBLE     HEAT     RECOVERY     AND 
THE     EFFECT     OF     OPERATING     CONDITIONS     NOT     CONSIDERED 


HOUSE  HEfTTING  BOILER 

—  BUREflU  OF  MINES  — 


<*0%  CHIMNEY  LOSS 

207o  UNCOVERED   PIPING 

5%     POOR  FIRING 

3  10%    DIRTy  FLUES 
-4XJ-257.     HEflT  TO  ROOMS 


CflRBURETTED  WflTER   GflS 


FUEL" 

—  VD.3.R.  CO.— 


-  ILL.  GEO.  SURVEY  - 


5%  WflSTE  QflS 
RflDlflTION -CTC, 

57.  TflR-rrc. 


£3%   CflRBONIZflTION 


6%  TO  10%  fl5H 
5%  TO  fc%  TflR 
LflMPBLflCK 


TflR   flND  BY-PRODUCTS 


22%  BLOW-UP   QflS   flND 
PROCESS  L055 


CflRDURETTED  WflTER  GflS 


117.  BLOW-UP  Gfl3 
71.  fl3H 

3.3%  SENSIBLE  HEflT 
BLUE   WflTER  Qfl5 

"FUEL"  GAS 


»«  BV  CONT^OV,  moce,,  mw*  HOT  cone 

TOR  WflTEK  GHS  flNO  BLOW-UP  G«  TO  MEBT  RtTO»TT3. 


POWER  PLflNT  (NON-CONDENSING)         5TEflM  POWER  PLflNT  (CONDENSING) 

—   RUPTAII    OF    Miwre  _  ._       *  ' 


—  BUREflU  OF  MINES  — 


30%    BOILER  L053 


-7.5%     flT  ENGINE  SHflFT 


STEflM  BOILER 

—  CURRENT  FRHCTICE  — 


MOISTURE 


15%  CHIMNEY   LOSS 


5%   RflDlflTION 
-707.    IN  STEflM 


60%    EXHflUST 


2.5%  FRICTION -ETC. 


SUCTION  PRODUCER  GflS  PLflNT 

—  R.O.  WOOD  CO.,  MODIFIED  — 


20%    PRODUCER   LOSS 
5%      FRICTION  flND  RflDlflTION 
.  EXMflUST 

^j  32%    COOLING 
fTT  ENGINE  ShflFT 


-  BUREflV  Of  MINES  - 


25%  BOILER  L033 


5B%   CONDENSER 


FRICTION  flNO  RflOlflTION 
-137.     flT  ENGINE  5HflFT 


COTTON  MILL  (flVERflGE) 

—  BUItEflU  Of  MINES,  MODIFIED  — 


35%  BOILER  LOSS 

57.     RflDlflTION 
67.     FRICTION 

CONDENSER 


*-l7.  flT  ENQINE  SHflFT 
*=====»  fe%     TRflNSMISSlON  LOSS 

•3%    ENERGY  UTILIZED 


GflS-ELECTRIC  PLflNT 

-  fl.S.M.E.  - 


20%   G05  PRODUCER 


n%   COOLINQ 


Y///A  30%    EXMflU5T 


77.     ENGINE  flND  QENERflTOR 
BUS   BflRS 


SUPER  STEflM- ELECTRIC  PLflNT 

—  BUREflU  OF  MINES  — 


ICE  MflKINQ  PLflNT 

-RS.R.E.— 


81  %  CONVERSION   LOSS 


BUS  BflR.5 


41 


30%   BOILER  LOSS 

lfc%     flUXILIflRIPS  flND  PIPING 

33%  CONDENSER 

FRICTION 
COMPRESSOR  LOSS 


-/k-157.    ICE  MflKINQ  EFFECT 


Fig. 


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UALITY  and  cost  of  heat-treated  products  are  greatly  influenced  by  type    layout  - 

P  We0™*      atmg  a^  ^^  e<?uiP™nt  and  form  of  heat  enJ^pod 

We  make  a  specialty  of  designing   and    constructing    modern   industrial 

fuel  or  electricity' for  the  2MS  <*££!? 

Our  practical  experience  of  over  thirty  years  is  illustrated  by  the  following  list  of 
'  "'  h""  buUt  '" 


ANNEALING   FURNACES.   Rolling    mill    type.      Improved   underfired 
downdraft  design   with  perforated   floor   to  permit  delivery  of 
heat  to  bottom  and  top  of  charge,  with  or  without  recuperation- 
improved  side-fired  design  for  comparatively  low  charges. 
Single  or  multi  chambers;  single  or  double  end;  all  sizes  for  ferrous 
and   non-ferrous   metals  in   form  of  ingots,   bars,   rods,   sheets, 
coils,  wire,  tubes,  etc.;  miscellaneous  stamped  or  drawn  parts 
such  as  cups,  shells,  etc.;  light  forgings,  castings,  etc. 
Automatic  conveyor,  revolving  (with  or  without  retort),  rotary 
table   and       beam"   types  for  ferrous  and  non-ferrous  pieces 
of  uniform  size  in  large  quantities,  with  provision  for  automatic 
charging,   preheating,  heating,  discharging,   quenching,  draining 
and  delivery,  as  required. 
Semi-automatic    pan    and    pusher    types    for    irregular    shapes 

carried  on  pans  or  trays,  or  regular  shapes  moved  on  rails. 
Bright   annealing  for  non-ferrous   metals;   continuous  conveyor 

type  with  water  seals;  pot  type  for  fine  wire,  etc. 
Car  type  with  removable  hearth  for  heavy  and  irregularly  shaped 

castings,  forgings,  etc. 
Car-and-ball  type  for  annealing  wire,  sheets,  etc.,  in  packing  boxes; 

heat-treatment  of  large  forgings,  castings,  etc. 
Removable  roof  type  for  steel  castings,  heavy  forgings,  etc. 
Side-opening  type  with  movable  partitions  to    accommodate  rela- 
tively small  parts  or  shafts  over  100  ft.  long. 
Stationary   type   with    single  or     multi  chambers,   with  or  without 

charging  machines  or  packing  boxes. 
Stoker-fired  type  for  miscellaneous  heavy  work. 

Direct  recuperative  type  for  recovery  of  heat  in  spent  gases  or  in 
outgoing  hot  charges  to  preheat  incoming  charge;   continuous 
or  intermittent  heating  and  handling. 
BAKING    FURNACES.     For    drying    wire,    miscellaneous    metal    pieces, 

heat-treating  chemical  products,  etc. 

BILLET  HEATING  FURNACES.  Continuous  and  intermittent 
types  for  ferrous  and  non-ferrous  ingots,  billets,  cakes,  etc.,  for 
rolling  or  forming;  heat-treatment  of  uniformly  shaped  pieces, 
such  as  car  axles,  etc.;  single  or  multi-chamber  design,  with 
different  arrangements  of  working  openings. 
BLAST  GATES.  Improved  air-tight  blast  gate  for  air,  etc.;  special 

types  for  liquids,  powders,  etc. 
BLOWERS.      Turbo,  positive  pressure  and  fan  types  for  air,  with  belt 

or  direct  motor  drive;  argand  or  turbo  types  for  steam. 
BLUING    FURNACES.      Continuous    and    stationary    types,    with   or 
without  muffles,  for  bluing  large  quantities  of  wire,  etc.;  auto- 
matic type  for  miscellaneous  small  parts. 
BRAZING  FURNACES.     For  tubes,  wire,  etc. 

BURNERS.  Oil  or  gas — 10  types  in  a  variety  of  sizes — for  high  pressure 
steam  and  high  or  low  pressure  air;  combination  types; 
special  types  for  mechanical  atomization  of  oil. 

CARBONIZING  FURNACES.  Single  and  multi-chamber  types, 
with  or  without  recuperation,  in  a  variety  of  sizes  with  different 
arrangements  of  chambers  and  working  openings;  special  types 
for  carbonizing  in  retorts  with  gas. 

CORE  OVENS.  Special  designs  in  large  sizes  with  movable  reels,  cars 
or  conveyors. 

CYANIDE  FURNACES.  Single  and  twin-pot  types,  with  or  without 
preheating  chambers. 

DRYING   FURNACES.      Rotary,   conveyor   and    stationary   types   for 

continuous  and  intermittent  operations,  with  or  without  muffles, 
for  metal  goods,  chemical  products,  etc. 

ELECTRIC  FURNACES.  Resistance  type  in  automatic,  semi-automatic 
and  stationary  designs  for  miscellaneous  heat-treatment  opera- 
tions on  metallurgical,  chemical,  ceramic  and  other  products 
requiring  accurate  control  of  chamber  atmosphere  and  tempera- 
ture. 

ENAMEL  FURNACES.  For  burning  and  melting;  standard  muffle  type 
for  coal,  oil  or  gas;  semi-muffle  type  for  intermittent  heating 
with  oil  or  gas  and  automatic  control  of  fire;  improved  down- 
draft  recuperative  type,  with  muffle,  for  bituminous  coal,  oil 
or  gas;  reverberatory  type  for  melting;  electric  resistance 
type  for  burning — continuous  or  intermittent  operation. 

FORGE  FURNACES.  Economizer  shield  type  to  protect  operator  and 
utilize  heat  from  working  opening  to  preheat  air  for  combustion. 
Single  or  double  end,  for  short  or  long  heats,  working  off  the 
bar  or  with  cut  stock  for  serving  drop  hammers,  upsetting 
machines,  rivet,  bolt  and  nut  machines,  etc.  Double  end  for 
long  rod  heating,  to  serve  continuous  rivet  and  bolt  making 
machines. 

Slot  and  magazine  types  for  bolt  heading. 

Miscellaneous  portable  types  for  short  end  heats,  tool  dressing,  etc. 
Blacksmith  type  for  general  work. 
Bulldozer  type  for  small  hammer  work. 


r  large  8team  ham™". 

~*" fuel  or  air- or  for  direct  recover* 

res   Continuous   and   int.rmUtent   typ.. 
GLASS  FURNACES.     For  melting  and  annealing  glass 
HARDENING   FURNACES.     Automatic,    semi-automatic    and    sta- 

h'£?£7a   HPh  *  !£•  a  vanetv  ?f  Si2es  with  different  methods  of 

HEATING  FURNACE^     r"8^3'  P°4  tyP*  ^  hardenin«  in  batl»- 

HtATING  FURNACES.  Continuous,  semi-automatic  and  station- 
ary types  for  miscellaneous  forming  operations 

HEAT-TREATING  FURNACES  Automaticf-emi-automatic  and 
stationary  types,  with  direct  or  indirect  heat  recovery-  size 
and  arrangement  of  chambers  and  working  openings,  methods 
t  heating  and  handling,  etc.,  adapted  to  individual  require- 
ments, using  coal,  oil,  gas  or  electricity;  semi-muffle  and 
muffle  types;  combination  types  for  continuous  annealing, 
normalizing,  hardening,  tempering,  etc. 

INCINERATING  FURNACES.  Special  type,  for  disposal  of  waste 
products. 

JAPANNING    FURNACES.     Continuous    and    stationary    type,    in 

large  sizes  for  special  drying  or  baking  operations. 

KILNS.     Special  designs  for  ceramic  products 

MELTING  FURNACES.  Stationary  and  tilting  crucible  and  rever- 
beratory types  for  non-ferrous  metals,  enamel  powder  and 
special  purposes. 

MUFFLE  FURNACES.  For  annealing,  enameling,  scaling,  rust-proofing, 
assaying  and  miscellaneous  purposes. 

OIL  APPLIANCES.  Burners;  oil  pumps;  relief  valves;  heaters;  unloading 
hose;  storage  tanks;  burner  plates;  blowers;  blast  gates;  special 
combustion  chamber  tiles;  etc. 

PATENTING  FURNACES.     For  continuous  heat-treatment  of  wire 

PLATE  HEATING  FURNACES.  For  miscellaneous  forming  operations 
in  ship,  railroad  and  boiler  shop  work;  angle  heating  type  for 
angles,  beams,  rods,  etc. 

Continuous  type  for  large  quantities  of  uniformly  shaped  pieces 
for  hot  press  work. 

POT  FURNACES.  Single  and  multi-pot  types,  with  or  without  pre- 
heating chambers,  for  heat-treatment  operations  in  baths  of 
oil,  lead,  salts,  etc.;  melting  soft  metals,  etc.,  with  or  without 
spout  and  valve  or  special  means  of  discharging  or  handling 
material;  special  types  for  bright  annealing,  carbonizing  and 
miscellaneous  processes. 

REGENERATIVE  AND  RECUPERATIVE  FURNACES.  For  high 
temperature  operations,  such  as  forging,  welding,  melting,  etc., 
utilizing  heat  in  spent  gases  to  preheat  air  and  fuel. 
Direct  recovery  type,  in  continuous  and  stationary  forms,  with 
single  or  multi  chambers,  utilizing  heat  in  spent  gases  or  hot 
charge  to  preheat  incoming  material. 

RE-HEATING  FURNACES  Intermittent  and  continuous  types, 
with  single  or  multi  chambers  or  doors. 

RETORT  FURNACES,  in  different  types  and  sizes,  with  metal  or  refrac- 
tory muffles. 

REVERBERATORY  FURNACES.     For  melting,  heavy  forging,  etc. 

RIVET  FORGES.      Portable  and  stationary  types. 

ROASTING  FURNACES.  Special  types  for  roasting  ores,  chemical 
products,  etc. 

ROD  HEATING  FURNACES.  Single  and  double-end  types  for  short 
or  long  heats. 

SCALING  FURNACES,  with  or  without  muffles,  for  ferrous  and  non- 
ferrous  metal  products. 

SHEET  AND  PAIR  FURNACES.      Continuous  and  stationary  types. 

SINGEING  FURNACES.  For  singeing  cloth,  carpet,  etc.,  with  hot 
plates  or  gas  flames. 

SPRING  FITTING  FURNACES.  Automatic,  semi-automatic  and 
stationary  types;  combination  fitting,  hardening  and 
drawing  stationary  type  for  vehicular  springs;  continuous 
and  stationary  types  for  one,  two  or  four  fitters  on  car  springs, 
etc. 

STOKER-FIRED  FURNACES.  With  or  without  recuperation,  for  mis- 
cellaneous heating  operations. 

TEMPERING  FURNACES.  Automatic,  semi-automatic  and  sta- 
tionary types  in  a  variety  of  designs  and  sizes;  special  types 
with  stationary  or  movable  dies  for  saws,  etc.;  miscellaneous 
designs  for  delicate  parts,  such  as  needles,  etc. 

TINNING  FURNACES.  Continuous  type  for  wire,  sheets,  etc.;  special 
types  for  long  tubes  and  miscellaneous  small  stamped  and  cast 
parts. 

TIRE  HEATING  FURNACES.  Stationary  and  continuous  types  for 
shrinking  operations. 

VARNISH  BOILING  FURNACES.     For  varnish,  oils,   gums,  greases,  etc. 


SPECIAL  DESIGNS  OF  FURNACES 

for 
Metallurgical,  Chemical,  Ceramic  and  Other  Processes 


43 


V    c^™ c**^ 
s&yVoS 


INDUSTRIAL  FUELS 
Comparative  Cost  Per  Million  B.  T.  U.  at  Unit  Prices 


BITUMINOUS  COAL 
at  $5.00  per  ton 

NATURAL    GAS 

at  25c  per  1000  cu.  ft. 

FUEL  OIL  at  5c  per  gal. 

ANTHRACITE  COAL 
at  $10.00  per  ton 

NATURAL  GAS 

at  40c  per  1000  cu  ft. 

*"FUEL"  GAS 

at  25c  per  1 000  cu.  f  t. 

FUEL  OIL  at  lOc  per  gal. 
KEROSENE  OIL 
at  lOc  per  gal. 

CITY  GAS 

at  50c  per  1000  cu.  ft. 

*"FUEL"  GAS 

at  50c  per  1000  cu.  ft. 

CITY  GAS 

at  $1.00  per  lOOOcu.ft. 
ELECTRICITY 

at  Ic  per  kw.  hr. 
GASOLINE 

at  30c  per  gal. 

ELECTRICITY 

at  2c  per  kw.  hr. 


Assumed  Thermal  Value 

B.  T.  u. 


Per 
Pound 


Per 
Cu.  Ft. 


Per 

Gallon 


FUELS 

Bituminous  Coal 15,000 

Anthracite  Coal 14,000 

Natural  Gas 950 

City  Gas 600 

*"Fuel"  Gas 400 

Fuel  Oil 142,000 

Kerosene 130,000 

Gasoline 85,000 

Electricity (3411  B.  t.  u.  =   1  kw.  hr.) 

*Gasification  by  continuous  process  utilizing  hot  coke  for  water   gas 
and  blow-up  gas  to  heat  retorts. 


1.67 


•  "  '  •  «-*-«-«  '  1           •            1           •           1 

i.l. 

$0.50         1.00                        2.00                        3.00 

4.00                         5.00 

6.00 

DOLLARS  PER  MILLION 

B.  T.  U. 

Fig.  28 

Quality  and  cost  of  finished  product — not  cost  of  fuel,  cost  of  labor,  mere 
tonnage,  nor  indication  of  uniform  chamber  temperature — are  the  determi- 
native tests  of  industrial  heating  operations. 


"FURNACE  AND   FUEL   TO   SUIT   CONDITIONS " 

is  our  rule  governing  consideration  of  new  or  improvement  of  existing  industrial  heating  equipment 
to  suit  your  needs  under  your  plant  conditions. 

We  make  inspection  of  plant,  devise  methods  of  heating  and  handling  material,  furnish  complete 
industrial  heating  equipment  adapted  to  your  particular  plant  conditions,  and  guarantee  results, 
using  coal,  oil,  gas  or  electricity,  as  your  best  interests  require. 


W.  S.  ROCKWELL  COMPANY 

Furnace  Engineers  and  Contractors 

50   CHURCH   STREET  NEW  YORK 


(Hudson  Terminal  Bldg.) 

Works:     NEWARK,  N.  J. 

Branches:        Chicago  Cleveland 


Detroit 


Ellsworth  Bldg.     Engineers'  Bldg.     Majestic  Bldg. 
Britith  Representative:       GIBBONS  BROS.,   Ltd.,       Dudley,  Wore.,  England 


44 


DEPARTMENT 


FORWNO.DD6,40m 


I 


